Green synthesis of nanometals using plant extracts and use thereof

ABSTRACT

The present invention relates to methods of making and using and compositions of metal nanoparticles formed by green chemistry synthetic techniques. For example, the present invention relates to metal nanoparticles formed with solutions of plant extracts and use of these metal nanoparticles in removing contaminants from soil and groundwater and other contaminated sites. In some embodiments, the invention comprises methods of making and using compositions of metal nanoparticles formed using green chemistry techniques.

FIELD OF THE INVENTION

The present invention relates to methods of making and using andcompositions of metal nanoparticles formed by green chemistry synthetictechniques. For example, the present invention relates to metalnanoparticles formed with solutions of plant extracts and use of thesemetal nanoparticles in removing contaminants from soil and groundwater.

Certain aspects of this invention were made with the support of theGovernment of the United States of America, and the Government may havecertain rights in the invention.

BACKGROUND

Nanoparticles are particles ranging in size from 1 nm to 1 micron indiameter. “Nano” is a prefix which means one billionth (10⁻⁹) part ofsomething (Meridian Webster Dictionary). In recent years, the field ofnanoparticles has grown due to their unique properties. Many industriesutilize nanoparticles, for example the electronics industry, medicalscience, material science, and environmental science. Noble metalnanoparticles have found widespread use in several technologicalapplications and various wet chemical methods have been reported. See,X. Wang and Y. Li, Chem. Commun., 2007, 2901; Y. Sun and Y. Xia,Science, 2002, 298, 2176; J. Chen, J. M. McLellan, A. Siekkinen, Y.Xiong, Z-Y Li and Y. Xia, J. Am. Chem. Soc., 2006, 128, 14776; J. W.Stone, P. N. Sisco, E. C. Goldsmith, S. C. Baxter and C. J. Murphy, NanoLett., 2007, 7, 116; B. Wiley, Y. Sun and Y. Xia, Acc. Chem. Res., 2007,40, 1067.

There is great interest in synthesizing metal and semiconductornanoparticles due to their extraordinary properties, which differ fromthose of the corresponding bulk material. An example of a nanoparticleis nanoscale zero valent iron (nZVI). Generally, nanoparticles aresynthesized in three ways: physically by crushing larger particles,chemically by precipitation, and through gas condensation. Chemicalgeneration is highly varied and can incorporate laser pyrolysis, flamesynthesis, combustion, and sol gel approaches. See, U.S. Pat. No.6,881,490 (2005-04-19) N. Kambe, Y. D. Blum, B. Chaloner-Gill, S.Chiruvolu, S. Kumar, D. B. MacQueen. Polymer-inorganic particlecomposites; J. Du, B. Han, Z. Liu and Y. Liu, Cryst. Growth and Design,2007, 7, 900; B. Wiley, T. Herricks, Y. Sun and Y. Xia, Nano Lett.,2004, 4, 2057; C. J. Murphy, A. M. Gole, S. E. Hunyadi and C. J.Orendorff, Inorg. Chem., 2006, 45, 7544; B. J. Wiley, Y. Chen, J. M.McLellan, Y. Xiong, Z-Y. Li, D. Ginger, and Y. Xia, Nanoletters, 2007,4, 1032; Y. Xiong, H. Cai, B. J. Wiley, J. Wang, M. J. Kim and Y. Xia,J. Am. Chem. Soc., 2007, 129, 3665; J. Fang, H. You, P. Kong, Y. Yi., X.Song, and B. Ding, Cryst. Growth and Design, 2007, 7, 864; A. Narayan,L. Landstrom and M. Boman, Appl. Surf. Sci., 2003, 137, 208; H. Song, R.M. Rioux, J. D. Hoefelmeyer, R. Komor, K. Niesz, M. Grass, P. Yang andG. A. Somorjai, J. Am. Chem. Soc., 2006, 128, 3027; C. C. Wang, D. H.Chen and T. C. Huang, Colloids Surf., A 2001, 189, 145. Examples ofmechanical processes for producing nanoparticles include mechanicalattrition (e.g., ball milling), crushing of sponge iron powder, andthermal quenching. Examples of chemical processes for producingnanoparticles include precipitation techniques, sol-gel processes, andinverse-micelle methods. Other chemical or chemically-related processesinclude gas condensation methods, evaporation techniques, gasanti-solvent recrystallization techniques, precipitation with acompressed fluid anti-solvent, and generation of particles from gassaturated solutions. The commercial significance of nanoparticles islimited by the nanoparticle synthesis process, which is generally energyintensive or requires toxic chemical solvents and is costly.

SUMMARY

The present invention relates to methods of making and usingcompositions of metal nanoparticles formed by green chemistry synthetictechniques, as well as the compositions themselves. For example, thepresent invention relates to metal nanoparticles formed with solutionsof plant extracts and use of these metal nanoparticles in removingcontaminants from soil and groundwater.

In one aspect, the invention provides methods for making metalnanoparticles. In some embodiments, the methods comprise providing adissolved metal ion, for example a metal ion in solution; providing aplant extract that comprises a reducing agent, a polyphenol, caffeine,and/or a natural solvent or surfactant; and combining the dissolvedmetal ion and the plant extract to produce one or more metalnanoparticles. For example, the dissolved metal ion can be provided bydissolving a metal salt in water. For example, the dissolved metal ioncan be provided by dissolving a metal chelate in water. For example, theproviding of the dissolved metal ion, the providing of a plant extract,and/or the combining of the dissolved metal ion and the plant extract toproduce one or more metal nanoparticles can be conducted at about roomtemperature and/or at about room pressure. For example, room temperaturecan be a temperature that is in a range that can be tolerated by humans.For example, a temperature greater than or equal to about that of thefreezing point of water and less than or equal to about the maximumtemperature that naturally occurs on the earth's surface can beconsidered to be room temperature. For example, a temperature of greaterthan or equal to about 0° C., 4° C., 10° C., 15° C., 20° C., 25° C., 30°C., 35° C., 40° C., 45° C., and 50° C. and less than or equal to about4° C., 10° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C.,50° C., and 60° C. can be considered to be room temperature. Forexample, room pressure can be pressure that is greater than or equal toabout the minimum that occurs on the earth's surface (includingmountaintops) and less that or equal to about the maximum that occurs onthe earth's surface (including below sea level depressions and thebottom of mines). For example, a pressure of greater than or equal toabout 20 kPa, 30 kPa, 50 kPa, 70 kPa, 90 kPa, 95 kPa, 100 kPa, 101 kPa,107 kPa, 120 kPa, 140 kPa, and less than or equal to about 30 kPa, 50kPa, 70 kPa, 90 kPa, 95 kPa, 100 kPa, 101 kPa, 107 kPa, 120 kPa, 140kPa, and 160 kPa can be considered to be room temperature. The metalnanoparticles can be present in a concentration effective for use in anapplication including, for example, soil and groundwater remediation,water and wastewater treatment, air pollution treatment, medicaldiagnostic testing, medical materials, targeted drug delivery, catalysisof chemical synthesis reactions, pollution control or monitoringdevices, fuel cells, or electronics. The dissolved metal ion can bepresent in an amount of, for example, at least about 0.01 mM, 0.1 mM,300 mM or more. The metal nanoparticles can be formed at a rate of, forexample, at least about 0.002 mol/L/min, at least about 0.01 mol/L/min,at least about 0.1 mol/L/min, at least about 0.5 mol/L/min or more,where “mol” refers to the moles of metal atoms that form the metalnanoparticles. The metal nanoparticles can have a mean diameter ofbetween about 5 and about 500 nm. A mass fraction of the metalnanoparticles that have a diameter between about 50 nm and about 100 nmcan be about 90 percent. The metal nanoparticles can have a meandiameter between about 20 and about 250 nm, or between about 50 andabout 100 nm. “Mean diameter” can refer to, for example, the weightaveraged mean diameter. That is, the mean diameter for a group ofparticles can be determined as the sum of the diameter of eachindividual particle weighted by its mass divided by the total mass ofthe particles. The reducing agent, polyphenol, caffeine, and/or naturalsolvent or surfactant can be one or more of, for example, tea extract,green tea extract, coffee extract, lemon balm extract, polyphenolicflavonoid, flavonoid, flavonol, flavone, flavanone, isoflavone, flavans,flavanol, anthocyanins, proanthocyanins, carotenoids, catechins,quercetin, and rutin. The natural solvent or surfactant can be, forexample, one or more of VeruSOL™-3, Citrus Burst 1 (CB-1), Citrus Burst2 (CB-2), Citrus Burst 3 (CB-3), and EZ-Mulse.

In some embodiments, the metal nanoparticles can comprise two or moremetals. Methods of making such metal nanoparticles can comprise, forexample, providing a dissolved metal ion; providing a plant extract thatcomprises a reducing agent, a polyphenol, caffeine, and/or a naturalsolvent or surfactant; providing a second dissolved metal ion, andcombining the dissolved metal ion, the second dissolved metal ion andthe plant extract to produce one or more metal nanoparticles eachcomprising a first and a second metal. The first and second dissolvedmetal ions can be added to the vessel more or less simultaneously,leading to nanoparticles in which the first and second metals areinterspersed throughout the metal nanoparticles. Or the first dissolvedmetal ion can be added to a vessel first and adding the second dissolvedmetal ion after a period of time, for example, of at least about 15 or30 seconds, for example, a period of time in the range of from about 30seconds to about 60 seconds, which generally leads to nanoparticles inwhich the first metal is present primarily in the core of the metalnanoparticle and the second metal is present primarily in an outer layeraround the core of the metal nanoparticle. The first metal can be, forexample, iron and the second metal can be, for example, palladium.Alternatively, palladium can be the first metal and iron can be thesecond metal.

In some embodiments, the dissolved metal ion can be, for example, adissolved iron ion or a dissolved manganese ion. The dissolved metal ioncan be provided by a species including, for example, a metal salt, aniron salt, ferric chloride (FeCl₃), ferrous sulfate (FeSO₄), ferricnitrate (Fe(NO₃)₃), a manganese salt, manganese chloride (MnCl₂),manganese sulfate (MnSO₄), a silver salt, silver nitrate (AgNO₃), apalladium salt, palladium chloride (PdCl₂), a metal chelate,Fe(III)-EDTA, Fe(III)-citric acid, Fe(III)-EDDS, Fe(II)-EDTA,Fe(II)-citric acid, Fe(II)-EDDS, and combinations thereof. The plantextract can be provided by a source including, for example, tea, coffee,parsley, sorghum, marjoram, lemon balm, and combinations thereof.Herein, unless otherwise stated, a source of plant extract is to beunderstood as referring to the product or material mentioned as well assources, plant components associated with sources, and processingintermediaries from which the product or material is derived, byproductsand waste resulting from manufacture of the product or material, andwaste following use or consumption of the product or material. Forexample, coffee as a source of plant extract can be construed to includea brewed coffee beverage as well as coffee fruit, coffee berries, coffeedrupes, coffee seeds, coffee beans, parts of the coffee plant, fermentedcoffee beans, coffee bean processing wastewater, roasted coffee beans,coffee bean chaff from roasting, ground coffee beans prior to brewing,coffee powder, dehydrated instant coffee powder, coffee groundsfollowing brewing, and coffee concentrate. For example, tea as a sourceof plant extract can be construed to include a brewed tea beverage aswell as tea plant buds, leaves, flushes, and other parts of a tea plant,fermented tea leaves, oxidized tea leaves, wilted tea leaves,post-fermented tea leaves, composted tea leaves, tea bricks, tea powder,instant tea powder, and tea leaf waste following brewing. In someembodiments, providing a plant extract involves combining a plant orplant portion with the dissolved metal ion in a vessel, causing, e.g., areducing agent, polyphenol, or caffeine to be released into the vesselto produce one or more metal nanoparticles.

In some embodiments, the methods also comprise providing an aqueoussolution of carboxy methyl cellulose, and combining the aqueous solutionof carboxy methyl cellulose with the dissolved metal ion and the plantextract to form metal nanoparticles coated with carboxy methylcellulose. The mixture of carboxy methyl cellulose, dissolved metal ion,and plant extract can be heated, for example to a temperature of about100° C., using a method such as exposing the mixture to microwaves. Insome embodiments, the dissolved metal ion is provided in situ, forexample by adding a chelating agent to a soil and/or water to betreated.

In some embodiments, the methods comprise providing a dissolved metalion; providing a plant derivative that comprises a reducing agent, apolyphenol, caffeine, and/or a natural solvent or surfactant; andcombining the dissolved metal ion and the plant derivative to produceone or more metal nanoparticles. The plant derivative can be, forexample, a plant extract or carboxy methyl cellulose.

In another aspect, the invention provides compositions. The compositionscan comprise, for example, a metal nanoparticle prepared according toany of the methods disclosed herein. The metal nanoparticle can be, forexample, coated with a substance derived from the plant extract used inthe preparation of the metal nanoparticle—i.e., the plant extract servesas a capping agent or dispersing agent for the nanoparticles. Thecomposition can also comprise a natural solvent or surfactant, such as,for example, VeruSOL™-3, Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2),Citrus Burst 3 (CB-3), EZ-Mulse, or combinations thereof. Thecomposition can also comprise a chelating agent, such as, for example,EDTA, EDDS, citric acid, or combinations thereof. The compositions canalso comprise an oxidant, such as, for example, peroxide, calciumperoxide, hydrogen peroxide, air, oxygen, ozone, persulfate, sodiumpersulfate, percarbonate, permanganate, or combinations thereof. Thecompositions can also comprise a carboxymethylcellulose coating or ahydrophobic coating on the surface of the metal nanoparticle. The metalnanoparticle can be, for example, a zero valent metal nanoparticle, azero valent iron nanoparticle, a zero valent manganese nanoparticle, asilver nanoparticle, a palladium nanoparticle, a gold nanoparticle, aplatinum nanoparticle, an iron nanoparticle, a manganese nanoparticle, acopper nanoparticle, an indium nanoparticle, or combinations thereof,and thus can also comprise at least two different metals, for exampleiron and palladium.

In still another aspect, the invention provides methods for reducing theconcentration of one or more contaminants in a medium. The methods cancomprise, for example, causing a metal nanoparticle prepared accordingto the methods described herein to be present in the medium; andallowing the metal nanoparticle to reduce or stimulate biologicalreduction of the contaminant to reduce its concentration. For example, acontaminant can be a chemical of concern (COC), such as a non-aqueousphase liquid (NAPL), dense non-aqueous phase liquid (DNAPL), and/orlight non-aqueous phase liquid (LNAPL). The metal nanoparticle can bepreviously prepared and thereafter introduced into the medium, or it canbe formed in situ, for example by introducing a reducing agent, apolyphenol, caffeine, and/or a natural solvent or surfactant into themedium; and allowing the reducing agent, polyphenol, caffeine, and/or anatural solvent or surfactant to react with the dissolved metal ions inthe medium to form metal nanoparticles. The methods can also compriseadministering a chelating agent, such as, for example, EDTA, citricacid, EDDS, or combinations thereof, to the medium. The contaminant canbe, for example, a perchlorate, nitrate, heavy metals or heavy metalcompounds, Hg²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cr₂O₇ ²⁻, AsO₄ ³⁻, compoundscomprising any of these, and combinations. The methods can also compriseintroducing a natural solvent or surfactant, such as, for example,VeruSOL™-3, Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3(CB-3), EZ-Mulse or combinations thereof, into the medium. The metalnanoparticle and the natural solvent and/or surfactant can be introducedinto the medium by injection into a subsurface. The methods can alsocomprise introducing an oxidant into the medium. The medium can be, forexample, a biologically contaminated material, soil, groundwater, water,wastewater, air, or combinations thereof.

In yet another aspect, the invention provides methods for determining anoptimal amount of dissolved metal ion to add to a plant extract solutionin synthesizing metal nanoparticles. The method can comprise providingseveral aqueous solutions of a first set having different concentrationsof a plant extract; adding DPPH to each aqueous solution of the firstset; determining DPPH absorbance of each aqueous solution of the firstset; adding a dissolved metal ion to several aqueous solutions of asecond set having different concentrations of the plant extract to formmetal nanoparticles; adding DPPH to each aqueous solution of the secondset comprising metal nanoparticles and remaining plant extract;determining DPPH absorbance of each aqueous solution of the second set;comparing the DPPH absorbance of the aqueous solutions of the first setand of the aqueous solutions of the second set to determine the netconsumption of DPPH; and determining the optimal ratio of dissolvedmetal ions to plant extract.

In still another aspect, the invention provides devices comprising ametal nanoparticle prepared according to any of the methods disclosedherein. The device can be, for example, a medical diagnostic test, amedical material such as a bandage, a targeted drug delivery vehicle, achemical synthesis system, a pollution control or monitoring device, afuel cell, and an electronic device.

DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a graph of specific conductivity as a function ofcumulative effluent volume in Column 1—Lemon Balm Extract with Fe(NO₃)₃.

FIG. 2 presents a graph of specific conductivity as a function ofcumulative effluent volume in Column 2—green tea extract with Fe(NO₃)₃.

FIG. 3 presents transmission electron micrographs of silver andpalladium nanoparticles in aqueous solutions of coffee and tea extractcast on a carbon coated copper grid. (a) Silver nanoparticles fromcoffee extract. (b) Silver nanoparticles from tea extract. (c) Palladiumnanoparticles from coffee extract. (d) Palladium nanoparticles from teaextract.

FIG. 4 presents TEM images of silver nanoparticles synthesized withcoffee and tea extracts.

FIG. 5 presents TEM images of palladium nanoparticles synthesized withcoffee and tea extracts.

FIG. 6 presents TEM images of Ag and Pd nanoparticles prepared inaqueous solutions using catechin.

FIG. 7 presents a graph of the spectra of absorbance as a function ofwavelength for a solution of tea extract with silver nitrate at varioustimes. (a) Pure tea extract. (b) After 1 min. (c) After 20 min. (d)After 40 min. (e) After 60 min. (f) After 2 hrs.

FIG. 8 presents a graph of UV-Visible spectra of Ag and Pd nanoparticlesin aqueous solutions of coffee and tea leaves extract. (a) Agnanoparticles from coffee extract. (b) Ag nanoparticles from teaextract. (c) Pd nanoparticles from coffee extract. (d) Pd nanoparticlesfrom tea extract. The inset shows UV-Visible spectra of (a) coffee and(b) tea extract.

FIG. 9 presents a graph of voltage as a function of time for coffeeextract in 1M sodium chloride solution.

FIG. 10 presents a graph of intensity as a function of 2 theta angle forsilver and palladium nanoparticles in coffee and tea extract. (a) Silvernanoparticles from coffee extract. (b) Silver nanoparticles from teaextract. (c) Palladium nanoparticles from coffee extract. (d) Palladiumnanoparticles from tea extract.

FIG. 11 presents TEM images of gold nanoparticles reduced with solutionsof catechin. 2 mL 0.01N solutions of gold ions reduced with: (a) 2 mL;(b) 4 mL; (c) 6 mL; and (d) 8 mL of catechin in (0.1N) aqueous solution

FIG. 12 presents TEM images of gold nanowires reduced with solutions ofcaffeine. 2 mL 0.01N solutions of gold ions reduced with (a) with 25 mg(b) 100 mg (c) 200 mg and (d) 300 mg of caffeine.

FIG. 13 presents a graph illustrating plant extract DPPH stable radicalconsumption from nanoscale zero valent iron particle formation fromreaction of green tea extract with ferric chloride.

FIG. 14 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M ferric chloride with 0 g/LVeruSOL™-3.

FIG. 15 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M ferric chloride with 2 g/LVeruSOL™-3.

FIG. 16 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M ferric chloride with 5 g/LVeruSOL™-3.

FIG. 17 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M ferric chloride with 10 g/LVeruSOL™-3.

FIG. 18 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M Fe(III)-EDTA with 0 g/LVeruSOL™-3.

FIG. 19 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M Fe(III)-EDTA with 5 g/LVeruSOL™-3.

FIG. 20 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M Fe(III)-citric acid with 0 g/LVeruSOL™-3.

FIG. 21 presents a micrograph of green tea synthesized zero valent ironnanoparticles made by combining 0.1 M Fe(III)-citric acid with 5 g/LVeruSOL™-3.

FIG. 22 presents a graph depicting UV spectra of (a) Fe, (b) tea extractand (c) reaction product of Fe(NO₃)₃ and tea extract. Inset shows thephotographic image of the reaction.

FIG. 23 presents a representative XRD pattern of iron nanoparticlessynthesized using tea extract.

FIG. 24 presents a graph depicting concentration-dependent bromothymolblue dye absorbance.

FIG. 25 presents a graph depicting UV-Vis Spectra (Absorbance versusWavelength) of bromothymol blue over time for an initial solutioncontaining 500 ppm bromothymol blue (pH 6), 2% H₂O₂, and 0.06 mMGT-nZVI.

FIG. 26 presents a graph depicting UV-Vis Spectra of bromothymol blueover time for an initial solution containing 500 ppm bromothymol blue(pH 6), 2% H₂O₂, and 0.33 mM GT-nZVI.

FIG. 27 presents a graph of concentration versus time depictingdegradation of bromothymol blue with GT-nZVI catalyzed H₂O₂. (a)bromothymol blue with 2% peroxide solution—control, (b) bromothymol bluetreated with 0.03 mM (as Fe) GT-nZVI catalyzed hydrogen peroxide (HP)(2%), (c) bromothymol blue treated with 0.06 mM (as Fe) GT-nZVIcatalyzed HP (2%), (d) bromothymol blue treated with 0.12 mM (as Fe)GT-nZVI catalyzed HP (2%), (e) bromothymol blue treated with 0.33 mM (asFe) GT-nZVI catalyzed HP (2%).

FIG. 28 presents initial rates, in In[BTB] vs. time, of decomposition ofbromothymol blue with GT-nZVI catalyzed H₂O₂. (a) bromothymol blue with2% peroxide solution—control, (b) bromothymol blue treated with 0.03 mM(as Fe) GT-nZVI catalyzed HP (2%), (c) bromothymol blue treated with0.06 mM (as Fe) GT-nZVI catalyzed HP (2%), (d) bromothymol blue treatedwith 0.12 mM (as Fe) GT-nZVI catalyzed HP (2%), (e) bromothymol bluetreated with 0.33 mM (as Fe) GT-nZVI catalyzed HP (2%).

FIG. 29 presents the initial rate constants for the decomposition ofbromothymol blue with GT-nZVI catalyzed H₂O₂ as a function of Feconcentration, expressed in terms of rate (min⁻¹) versus GT-nZVIconcentration (mM) as Fe (y=0.4694x−0.0106R²=0.9989).

FIG. 30 presents the degradation of bromothymol blue concentration overtime with Fe-EDTA and Fe-EDDS catalyzed H₂O₂. (a) bromothymol bluetreated with 0.12 mM Fe catalyzed HP (2%), (b) bromothymol blue treatedwith 0.33 mM as Fe catalyzed HP (2%), (c) bromothymol blue treated with0.50 mM as Fe catalyzed HP (2%), (d) bromothymol blue treated with 0.66mM as Fe (Fe-EDDS only) catalyzed HP (2%).

FIG. 31 presents the initial rates, expressed in terms of In[BTB] versustime, of decomposition of bromothymol blue with Fe-EDTA and Fe-EDDScatalyzed H₂O₂. (a) bromothymol blue treated with 0.12 mM Fe catalyzedHP (2%), (b) bromothymol blue treated with 0.33 mM as Fe catalyzed HP(2%), (c) bromothymol blue treated with 0.50 mM as Fe catalyzed HP (2%),(d) bromothymol blue treated with 0.66 mM as Fe (Fe-EDDS only) catalyzedHP (2%).

FIG. 32 presents the initial rate constants for the decomposition ofbromothymol blue as a function of Fe concentration, with Fe-EDTA andFe-EDDS: Rate (min⁻¹) vs Fe-EDTA or Fe-EDDS (mM) as Fe. Fe-EDTA:y=−0.0016x+0.0043 (R²=0.9963), Fe-EDDS: y=−0.0099x+0.0164 (R²=0.7135).

FIG. 33 presents a graph depicting the concentration dependentabsorption of bromothymol blue (pH <6) (Standard curve).

FIG. 34 presents a series of graphs depicting a time-dependent Au-10reaction after (a) 0 minutes (control); (b) 1 minute; (c) 2 minutes; and(d) 3 minutes.

FIG. 35 presents UV spectra of (a) Au-8 (b) Au-3 and (c) Au-13 samples.

FIG. 36 presents UV spectra of (a) Au-15, (b) Au-5 and (c) Au-10samples.

FIG. 37 presents UV spectra of (a) Au-7 and (b) Au-12 samples.

FIG. 38 presents UV spectra of (a) Au-11, (b) Au-1 and (c) Au-6 samples.

FIG. 39 presents XRD patterns for (a) Au-4, (b) Au-9, (c) Au-14, (d)Au-1, (e) Au-11, (f) Au- 5, (g) Au-10 and (h) Au-8.

FIG. 40 presents SEM images of (a) Au-1, (b) Au-2 and (c-d) Au-4samples.

FIG. 41 presents SEM image of (a) Au-11 (b) Au-12 and (c-d) Au-14samples.

FIG. 42 presents SEM images of (a) Au-6 (b) Au-8 (c) Au-9 and (c) Au-10samples.

FIG. 43 presents representative EDX spectra of Aux nanostructuresobtained using an Au-6 sample.

FIG. 44 presents TEM images of (a-b) Au-1, (c) Au-2 and (d) Au-5samples.

FIG. 45 presents TEM image of (a-b) Au-3 and (c-d) Au-4 samples.

FIG. 46 presents XRD patterns for butyl ammonium bromide-reduced Aunanostructures.

DETAILED DESCRIPTION

Embodiments of the invention are discussed in detail below. Indescribing embodiments, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected. A person skilled in the relevant artwill recognize that other equivalent parts can be employed and othermethods developed without parting from the spirit and scope of theinvention. All references cited herein are incorporated by reference asif each had been individually incorporated. For example, U.S. Appl. No.12/068,653 and U.S. Prov. Appl. No. 61/071,785 are hereby incorporatedby reference.

“Introduce” means to cause to be present in a location. A material oritem can be introduced into a location even if the material or item isreleased somewhere else and must travel some distance in order to reachthe location. For example, if a substance is released at location A, andthe substance will migrate over time to location B, the substance hasbeen “introduced” into location B when it is released at location A. Anitem can be introduced in any manner appropriate under the circumstancesfor the substance to be introduced into the location.

“Effective” means sufficient to accomplish a purpose, and “effectiveamount” or “effective concentration” means an amount or concentrationsufficient to accomplish a purpose. The purpose can be accomplished byeffecting a change, for example by decreasing the concentration of acontaminant in a location to be remediated. A purpose can also beaccomplished where no change takes place, for example if a change wouldhave taken place otherwise.

“Plant derivative” encompasses any portion of a plant that can be usedaccording to the purposes of the present invention, for example to bringabout the formation of metal nanoparticles from dissolved metal ions.“Plant derivative” encompasses, for example, “plant extract.” As usedherein, a “plant extract” encompasses, for example, any chemical orcombination of chemicals found in a plant or that can be prepared usinga chemical or chemicals found in a plant, whether by preparingderivatives of the compounds found in the plant via chemical reaction.As used herein, “plant derivative” also encompasses carboxy methylcellulose.

As used herein, “nano-sized” and “nano-scale” mean particles less thanabout 1 micron in diameter, though a different meaning may be apparentfrom the context. As used herein, “micro-sized” and “micro-scale” meanparticles from about 1 to about 1000 microns in diameter. As usedherein, “macro-sized” and “macro-scale” mean particles greater thanabout 1000 microns in diameter. A “nanoparticle” is a particle whosediameter falls within the nano-scale range. A nanoparticle can bezero-valent, or it can carry a charge.

As used herein, “medium” encompasses any location or item in whichcontaminants can be found. For example, “medium” includes, withoutlimitation, a biologically contaminated material, soil, groundwater,water, wastewater, air, and combinations thereof.

“Contaminants” encompasses any substance present in a location that, byits presence, diminishes the usefulness of the location for productiveactivity or natural resources, or would diminish such usefulness ifpresent in greater amounts or if left in the location for a length oftime. The location may be subsurface, on land, in or under the sea or inthe air. As used herein, “contaminated soil” encompasses any soil thatcontains at least one contaminant according to the present invention.“Contaminant” thus can encompass trace amounts or quantities of such asubstance. Examples of productive activities include, withoutlimitation, recreation; residential use; industrial use; habitation byanimal, plant or other life form, including humans; and similar suchactivities. Examples of natural resources are aquifers, wetlands,sediments, soils, plant life, animal life, ambient air quality.

A “vessel” is any container or location that is capable of supportingthe reactions and preparative methods disclosed herein. For example, avessel can be a beaker, column, pot, mixing apparatus, vat, or any otherlaboratory or manufacturing apparatus that can hold gases, liquidsand/or solids. As used herein, a “vessel” can also be a location in needof remediation.

As used herein, “plant portion” means any part of a plant that can beused as a source of reactants in the nanoparticle preparation methodsdisclosed herein. For example, sorghum is very rich in phenolics, suchthat it is generally not necessary to perform an extraction before usingsorghum phenolics in the preparation of metal nanoparticles. Instead, itis possible to prepare nanoparticles simply by placing a sorghum plant,or portion thereof, into the reaction vessel. Examples of “plantportions” include, for example, the husk, stem, root, leaves, flower,fruit, seed, or any other part of the plant.

Conventional methods for manufacturing metal nanoparticles, such as nZVIor nZVMn, include milling and solution methods. Many conventionalmethods, for example the high energy milling method, involve the use oftoxic solvents and industrial surfactants to prevent oxidation of iron,for example during the crushing operation. Solution methods use toxicinorganic chemicals, including strong chemical reducing agents such assodium borohydride, dispersing agents, and stabilization agents. Sodiumborohydride, a commonly used reducing agent use to make zero valent ironnanoparticles, is a highly hazardous material. After making zero valentiron nanoparticles using sodium borohydride, the sodium borohydride mustbe washed from the zero valent iron nanoparticles, resulting in thegeneration of liquid hazardous wastes.

By contrast, the invention encompasses green methods of making metalnanoparticles, such as zero valent metal nanoparticles, including greenchemistry methods. Green chemistry is the design, development, andimplementation of chemical products and processes for the purpose ofreducing or eliminating the use and generation of substances hazardousto human health and the environment. See, P. T. Anastas and J. C.Warner, Green Chemistry: Theory and Practice; Oxford University Press,Inc.: New York, 1998. To address mounting environmental concernsregarding conventional approaches, green chemistry methods involve theuse of environmentally benign solvents, biodegradable polymers, andnon-toxic chemicals.

In an embodiment of the invention, metal nanoparticles are synthesizedby reducing the corresponding metal ion salt solutions. Green chemistrycan be employed, for example, in the (i) choice of solvent, (ii) thechoice of reducing agent, and (iii) the choice of capping agent (ordispersing agent) used. Multifunctional environmentally-friendlymaterials can be used in synthesizing metal nanoparticles. For example,tea and/or coffee extract, which can contain polyphenols, can functionboth as a reducing agent and a capping agent in producing, e.g., silver(Ag), palladium (Pd), gold (Au) and iron (Fe) nanoparticles. Caffeineand/or polyphenols can form complexes with metal ions in solution andreduce them to the corresponding metals. Nanoparticles, e.g. of noblemetals, transition metals, manganese (Mn), copper (Cu), gold (Au),platinum (Pt), and indium (In) can be produced with this method. Thenanoparticles can be of zero valent metal. Tea and coffee extracts havehigh water solubility and low toxicity and are biodegradable.

In an embodiment of the invention, bulk quantities of nanoparticles, ornanocrystals, of metals such as transition metals, noble metals, silver(Ag), gold (Au), platinum (Pt), palladium (Pd), and iron (Fe), manganese(Mn), copper (Cu), and indium (In) are produced in a single pot methodusing coffee and/or tea extract, e.g., green tea extract, at roomtemperature. The nanoparticles can be of zero valent metal. Thenanoparticles can be produced without a separate surfactant, cappingagent, or template. The nanoparticles obtained can have a size range offrom about 5 to about 500 run, for example about 20 to about 60 nm andcan be crystallized in face centered cubic symmetry. Size can beunderstood as diameter of a nanoparticle. For example, diameter can bethe volume diameter, that is (6V/π)^(1/3), where V is the volume of thenanoparticle. Plant extracts containing high concentration of reducingagents, including polyphenolic compounds can be used to synthesizenanometal particles in addition to those from tea and coffee can beused. For example, extracts of parsley, sorghum, marjoram, aronia,crowberry, spinach, potato, beets, spruce needles, willowherb, rosemary,meadowsweet and lemon balm can be used to produce nanometals at roomtemperatures and pressures, without the use of toxic or hazardouschemicals or the production of wastes containing toxic or hazardouschemicals. Sources of compounds useful for producing metal nanoparticlescan include, for example, berries, fruits, vegetables, herbs, medicalplants, cereals, and tree materials. Waste products, process streams, orby-products from plant processing containing high concentrations ofplant polyphenols can be used. The materials can include fruit juicepulp, fruit juice manufacturing wastewater, fruit juice manufacturingwaste, food processing waste or byproduct materials, wine and beermanufacture and forest product processing waste streams. Compoundsuseful for producing metal nanoparticles can include polyphenols,antioxidants, radical scavengers, polyphenolic flavonoids, flavinoidphenolic compounds, flavinoids, flavonoids, flavonols, flavones,flavanones, isoflavones, flavans, flavanols, anthocyanins,proanthocyanins, carotenoids, catechins, quercetins, rutins, catechins,epicatechins and their esters from ferulic and gallic acids, e.g.epigallocatechin. Antioxidant compounds that can be useful for metalnanoparticle synthesis include natural antioxidants such as flavonoids,e.g., quercetin, glabridin, red clover, and Isoflavin Beta (a mixture ofisoflavones available from Campinas of Sao Paulo, Brazil). Otherexamples of natural antioxidants that can be used as antioxidants forsynthesizing metal nanoparticles include beta carotene, ascorbic acid(vitamin C), vitamin B1, vitamin B2, tocopherol (vitamin E) and theirisomers and derivatives. Non-naturally occurring antioxidants, such asbeta hydroxy toluene (BHT) and beta hydroxy anisole (BHA), can also beused to synthesize metal nanoparticles. Plant oil based surfactants canbe used to synthesize metal nanoparticles, such as polyethylene glycol(PEG) modified plant oils. Plant oils such as castor oil, corn oil, palmoil, coconut oil, canola oil, cottonseed oil, almond oil, olive oil,rapeseed oil, peanut oil, safflower oil, sesame oil, sunflower oil, acaioil, flax seed oil, hemp oil and algae-derived oil.

Plant extracts that are U.S. FDA Generally Recognized as Safe (GRAS) canbe used. The synthesis of metal nanoparticles, such as zero valent ironnanoparticles, with natural resources, can avoid generating hazardouswaste and thus can reduce environmental risk. Methods for making metalnanoparticles with plant-based extracts can be easier and safer thanconventional methods of making metal nanoparticles.

The green synthesized nanoparticles and compositions including thesenanoparticles according to embodiments of the invention can be used, forexample, to remediate contaminated sites by inducing chemical reductionmechanisms, by stimulating biological reduction mechanisms, or by acombination of chemical and biological reduction mechanisms. Forexample, the green synthesized nanoparticles, including zero valentnanometal particles and bimetallic particles, can serve as reducingagents in processes to detoxify inorganic species, such as metals, heavymetals, arsenical compounds, and chromium compounds, e.g., Hg²⁺, Ni²⁺,Ag⁺, Cd²⁺, Cr₂O₇ ²⁻, and AsO₄ ³⁻, by in-place manufacture and treatment.The green synthesized nanoparticles, e.g., zero valent nanometalparticles, can be used as reducing agents to destroy oxidizing agentcompounds such as perchlorates (ClO₄ ⁻) and nitrates (NO₃ ⁻). The metalnanoparticles can be administered with, for example, plant derivedreducing agents, in order to increase the reducing effect of thenanoparticles on the species to be remediated.

The nanoparticles and compositions including them can be used forcatalysis, for example, to activate free radical oxidation chemistriesfor remediation, water treatment, and wastewater treatment. Greensynthesized nanoparticles, such as nZVI or nZVMn particles, andcompositions including them can be applied to remediate sitescontaminated with, for example, non-aqueous phase liquids (NAPLs), densenon-aqueous phase liquids (DNAPLs), and/or light non-aqueous phaseliquids (LNAPLs). The green synthesized nanoparticles can be appliedtogether with VeruTEK's VeruSOL™ green co-solvents and surfactantsand/or oxidants. For example, the metal nanoparticles can be appliedwith oxidants such as peroxide (e.g., calcium peroxide, hydrogenperoxide), air, oxygen, ozone, persulfate (e.g., sodium persulfate),percarbonate, and permanganate. The green synthesized nanoparticles canbe used, for example, to remediate contaminated water, wastewater,building materials and equipment, and subsurfaces. nZVI can be producedwith green tea and ferric chloride in the presence or absence ofVeruSOL™-3. Similarly, nZVI can be produced with green tea and chelatediron in the presence or absence of VeruSOL™-3.

The nanoparticles according to the invention and compositions includingthem can be applied in conjunction with, for example, catalyzed oxidantsystems or reduction technologies to destroy DNAPL or LNAPL compounds.Thus, nanoparticles according to the invention and compositionsincluding them can be used, for example, to treat CERCLA Sites, NPDESpermitted discharges, and RCRA Sites. Furthermore, systems regulatedunder the Safe Drinking Water Act, Clean Water Act, FIFRA, and TSCA canbe treated using nanoparticles according to the invention andcompositions including them. For example, agencies of the U.S.Government, such as the Department of Defense, are responsible for sitesthat can benefit from treatment with materials according to theinvention, such as nanoparticles and compositions including them. Use ofthe materials according to the invention to treat water, wastewater, andcontaminated soils can reduce risks to the public and environment.

For example, green synthesized silver or composite silver nanometalsaccording to the invention can be used to disinfect materials anddisinfect biological agents. Such silver or composite silver nanometalscan be, for example, incorporated into medical materials to providedisinfecting properties. Metal nanoparticles can have additional medicalapplications.

Nano-scale zero valent iron (nZVI) is of increasing interest for use ina variety of environmental remediation, water and waste water treatmentapplications. Initial ZVI research used microscale (≃150 μm) particlesfor environmental applications in reactive subsurface permeable barriers(PRBs) for chemical reduction of chlorinated solvents. In comparison tolarger sized ZVI particles, nZVI has a greater reactivity due to agreater surface area to volume ratio. Recent environmental applicationsinclude removal of nitrite by ultrasound dispersed nZVI, dechlorinationof dibenzo-P-dioxins, reduction of chlorinated ethanes, adsorption ofhumic acid and its effect on arsenic removal and hexavalent chromiumremoval. However, field applications of ZVI have been limited togranular particles used in permeable reactive barriers (PRB). While PRBsare found to be effective for the remediation of shallow aquifers, morecost-effective in situ technologies are needed for rapid and completedestruction of chlorinated contaminants in deep aquifers and in sourcezones. However, for this technology to be feasible, the nZVI particlesmust be small enough to be mobile in the targeted zones, and thetransport behaviors (or size) of the nanoparticles in various soils mustbe controllable.

A technique for preparing nZVI particles of controlled size andtransport properties was previously unavailable, and a method is lackingto extend the reactive lifetime of these relatively short-livednanoparticles. Their extreme reactivity is addressed in thisinvestigation, as the relative stability of such nZVI particles has beenenhanced using tea polyphenols which cap the ensuing nanoparticles.Table 1 presents examples of green tea manufacture of nanoscale zerovalent iron particles, for example with cosolvent-surfactant mixtures,ferric chloride and chelated iron.

TABLE 1 Green Tea Manufacture of Nanoscale Zero Valent Iron Particleswith Cosolvent-Surfactant Mixtures, Ferric Chloride and Chelated IronTesting Conditions Chemical doses Total Chumnee T.E. FeCl₃ Volume VS-3(20 g/L) (0.1M) Fe-EDTA Fe-Citric Acid Sample ID ml g/L mL mL 0.1M as Fe0.1M as Fe Tea NZVI-T1 480 2 160 320 — — Tea NZVI-T2 480 5 160 320 — —Tea NZVI-T3 480 10 160 320 — — Tea NZVI-T4 480 0 160 320 — — Tea NZVI-T5480 0 160 — 320 — Tea NZVI-T6 480 5 160 — 320 — Tea NZVI-T7 480 0 160 —— 320 Tea NZVI-T8 480 5 160 — — 320

Gold nanostructures have been the focus of intense research owing totheir fascinating optical, electronic, and chemical properties andpromising applications in nanoelectronics, biomedicine, sensing, andcatalysis. A variety of methods have been developed to fabricate goldnanoparticles using NaBH₄, microwave, simple galvanic replacementreaction (transmetalation reaction), polymeric strands ofoleylamine-AuCl complexes, poly(vinyl pyrrolidone) (PVP) in aqueoussolutions, reducing agent (ascorbic acid), seed-mediated synthesis andionic polymers. Wet methods often require the use of an aggressivechemical reducing agent such as sodium borohydride, hydroxylamine,and/or a capping agent and may additionally involve an organic solventsuch as toluene or chloroform. Although these methods may successfullyproduce pure, well-defined metal nanoparticles, the cost of productionis relatively high both materially and environmentally. Consequently,more cost-effective and environmentally benign alternatives to theseexisting methods should be developed. The choice of an environmentallycompatible solvent system, an eco-friendly reducing agent, and anonhazardous capping agent for the stabilization of the nanoparticlesare three main criteria for a totally “green” nanoparticle synthesis.Recently, there has been an increased emphasis on the topics of “green”chemistry using environmentally benign and renewable materials as therespective reducing and protecting agents. The use of environmentallybenign and renewable materials in the production of metal nanoparticlesis important for pharmaceutical and biomedical applications.

In addition to their uses in remediation applications, metalnanoparticles prepared according to embodiments of the invention can beuseful in a wide variety of fields. For example, gold nanoparticleapplications include the following: due to the low oxidation metalpotential associated with gold nanoparticles, gold nanoparticles can beused in medical diagnostic tests, such as, labeling, immunostain, x-raycontrasting, and phagokinetic tracking studies; targeted drug deliverytechniques, for example conjugated with ligands or proteins, and alsothose involving gene guns, uptake by cells, and as a heat source to killselected cells such as cancer using targeting cell hypothermia,optically triggered opening of DNA bonds. Gold nanoparticles withphytochemical coatings have shown significant affinity toward prostate(PC-3) and breast (MCF-7) cancer cells.

Gold nanoparticles are valuable catalysts in chemical synthesisreactions and for pollution control devices, such as those involving (1)colorimetric detection methods for cysteine basedoligonucleotide-functionalized gold nanoparticle probes that containstrategically placed thymidine-thymidine (T-T) mismatches to complexHg²⁺ ions; and (2) colorimetric metal sensors based on DNAzyme-directedassembly of gold nanoparticles and their use for sensitive and selectivedetection and quantification of metal ions, particularly lead in leadedpaint. Fuel cell applications include use of gold nanoparticles oncarbon supports. Electronic devices also use gold nanoparticles forsuperior conductance. Other uses for metal nanoparticles include cancercell and DNA hypothermic inactivation, biological agent inactivation,full cells, and toxicity reduction.

In some embodiments, the reducing agent used in preparing the metalnanoparticles can be, without limitation, a phenolic compound, aphenolic plant extract, a plant extract-based surfactant, a naturalsolvent or surfactant, a plant oil based surfactant, a flavonoid, orcombinations thereof. In some embodiments, the reducing agent isextracted using a plant-based solvent, such as d-limonene and citrusterpenes.

In some embodiments, the plant extract and/or reducing agent is furtherconcentrated for example prior to use in the preparation of metalnanoparticles. The concentration process can produce a higherconcentration of plant polyphenols, enabling a high concentration ofdissolved metal to be used to make higher concentrations of nanometalparticles. The plant extract and/or reducing agent can be concentratedusing any method known in the art, for example using reverse osmosisand/or filter presses or using extraction with supercritical carbondioxide. Similarly, the green synthesized nanometal particles can befurther concentrated, for example after they are prepared, to producehigher concentrations of nanometal particles. Concentration methodsinclude, but are not limited to, centrifugation, filtrations, magneticseparation, electroosmosis, and electrokinetic migration.

Free radicals initiated from catalysis or activation of hydrogenperoxide or sodium persulfate can be readily experimentally determinedusing probe compounds such as bromothymol blue. Bromothymol blue has anadvantage over methylene blue as a probe compound as it is not directlyoxidized (in the absence of free radicals) by sodium persulfate.Methylene blue is directly oxidized by sodium persulfate, therefore itcannot be used to experimentally determine free radical generation andsubsequent destruction by sodium persulfate. The advantage ofbromothymol blue is that it is not directly oxidized by either hydrogenperoxide or sodium persulfate.

In the process of experimentally optimizing the initiation andgeneration of free radicals using various catalysis or activators,bromothymol blue is superior to many other probe compounds in thatvarious catalysts and activators can be rapidly evaluated. For example,Fe-chelated metal catalysts such as Fe-TAML, Fe-EDTA, Fe-EDDS, Fe-EDDHA,Fe-EDDHMA, Fe-EDDCHA, Fe-EDDHSA, Fe-NTA, and Fe-DTPA can be used ascatalysts for peroxide and persulfate. Other transition metal catalystscan also be used, such as Mn, Co, Ni, Cu, and Zn. Additionally,nanoparticle catalysts, such as nanoiron, bimetallic nanoiron speciessuch as Fe/Ni, Fe/Pd, Fe-oxides, Mn-oxides, silicates, alumina, andmixed transition metal oxides, can be used.

In many industrial applications, the faster the catalysis of peroxideand persulfate the better. However, the catalysis of peroxide andpersulfate in subsurface remediation applications is best conducted at acontrolled rate and in many cases as slow as possible, while stillmaintaining effective catalysis. Slowing the catalysis rates using plantextract and plant extract-based surfactants is effectively achieved andthe desired rate obtained using bromothymol blue as a probe compound.Inclusion of plant extracts can reduce the rate of catalysis to, forexample, 90%, 75%, 50%, 25%, 10%, 5%, 1% or less, compared to the ratewithout plant extract-containing catalysts. In terms of initial rateconstants, the plant extract-controlled catalysts may decrease theinitial rate constant to 0.2/min, 0.1/min, 0.05/min, 0.01 /min,0.005/min or otherwise as described for a particular application.

In some embodiments, the invention provides methods of using bromothymolblue as a probe compound. Bromothymol blue can be used, for example, tooptimize the rate of peroxide or persulfate catalysis, for exampleusing: a) bromothymol blue; b) a catalyst or mixture of catalysts, andoptionally one or more of c) an oxidant stabilizer; d) a catalyststabilizer; e) a soil sample; and/or f) a contaminant.

Examples of oxidant stabilizers include, without limitation, plantextracts, surfactants including, for example, plant-extract basedsurfactants, and/or plant extract solvents and cosolvents. Examples ofcatalyst stabilizers include, without limitation, plant extracts,surfactants including, for example, plant-extract based surfactants,chelates, poly(ethylene terephthalate), poly(amidoamine)-dendrime,polyethylene glycol and nanometal capping agents. In addition, thenanometal particle morphology can be optimized for the formation of freeradicals in peroxide and/or persulfate catalysis.

A DPPH test can be used to measure the gross antioxidant capacity ofplant extracts. DPPH (2,2-diphenyl-1-picrylhydrazyl) is a stable freeradical in an aqueous solution. When a plant extract in solution isexposed to DPPH, the amount of DPPH decreases according to theantioxidant capacity of the plant extract. Generally, the more DPPHconsumption, the greater concentration of plant extract components,e.g., polyphenols. The more plant extract components, e.g., polyphenols,are in solution, the greater their capacity to make nanometal particles.A DPPH test can be used to determine which plant extracts, and underwhat extraction conditions, yield the highest concentration of plantextract components, e.g., polyphenols for use in making nanometalparticles.

The metal ions in solution can be within a range of, for example, fromabout 0.001 M to 1.0 M, or about 0.01 to 0.1 M, for example, up to or atleast about 0.001 M, 0.005 M, 0.01 M, 0.05 M, 0.1 M, 0.2 M, 0.3 M, 0.4M, 0.5 M, 0.6 M, 0.7 M, 0.8 M, 0.9 M, 1.0 M or more. The plant extractcan have a concentration of, for example, from about 5 g/L to about 200g/L, or about 10 g/L to about 100 g/L, or about 15 g/L to about 50 g/L,or about 40 g/L to about 100 g/L, or up to or at least about 0.1, 0.5,1, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140,150, 160, 170, 180, 190, 200 g/L or more. The metal nanoparticles can bepresent in a concentration of from about 0.0006 to about 0.6 M, about0.005 to about 0.1 M, or up to or at least about 0.0001, 0.0005, 0.001,0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 M, 1 M or more. Thenanoparticles can have a diameter of, for example, from about 1 nm toabout 1000 nm, from about 5 nm to about 100 nm, about 20 nm to about 85nm, about 10 to about 50 nm, about 40 to about 100 nm, or up to or atleast about 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm,80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 250 nm,300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or more.

The nanoparticles can have various shapes, including spheres, rods,prisms, hexagonal and mixed prisms, faceted shapes, wires, and othershapes.

In some embodiments, the amount of the plant extract used in the methodsdisclosed herein is sufficient to convert substantially all of thedissolved metal ion into nanoparticles. As used herein, “substantiallyall” encompasses, e.g., greater than 50%, or at least about 60%, 70%,80%, 85%, 90%, 95% or more. Different meanings of “substantially all”may be apparent from the context.

Compositions comprising metal nanoparticles can comprise, for example,metal nanoparticles and plant extract or components of plant extracts insolution; metal nanoparticles having a component of a plant extract,including, without limitation, one or more phenolic compounds, on itssurface; with a component of a plant extract, including, withoutlimitation, one or more phenolic compounds, interspersed within themetal nanoparticle. In addition, compositions comprising metalnanoparticles can also be compositions from which liquid components havebeen removed, for example through filtration or another method, suchthat the particles are suitable for, e.g., packaging and shipping; aconcentrated form of a composition comprising nanoparticles in a liquid;as well as other forms, as would be appreciated by a person of ordinaryskill in the art.

The metal nanoparticles according to the invention can be characterizedby having a high degree of dispersibility. For example, the metalnanoparticles can be much easier to handle because they are lesssusceptible to aggregation than are metal nanoparticles prepared usingother methods. For example, if the metal nanoparticles preparedaccording to embodiments of the invention are isolated, e.g., throughfiltration, and then later redispersed in, for example, water, theparticles will be less susceptible to aggregation upon redispersion thanare nanoparticles prepared using other methods. Nanoparticles preparedaccording to other methods often require the application of a cappingagent. Metal nanoparticles prepared according to embodiments of theinvention generally do not require such an additional step.

As used herein, a “natural solvent or surfactant” is a substance orcomposition that can perform, e.g., one or both of two functions. First,a natural solvent or surfactant can be a substance or composition thatcan be used to reduce metal ions in solution in the preparation of metalnanoparticles, such as zero-valent metal nanoparticles. Second, anatural solvent or surfactant can serve to reduce the surface tensionbetween two phases, for example between an aqueous phase and anon-aqueous phase that contains, e.g., a contaminant or other substanceto be remediated.

Nanoparticles, for example isolated nanoparticles, may be incorporatedinto any device in which nanoparticles as disclosed herein may be used.

EXAMPLE 1 Green Synthesis Manufacture of Nanoscale Zero Valent Iron(NZVI) or Manganese (NZVMn)

A method according to the invention uses plant extracts containingreducing agents that are capable of forming nanoparticles in thepresence of dissolved iron species. The reactions are nearlyinstantaneous when plant extracts containing reducing agents are mixedwith dissolved iron or manganese species. The plant reducing agentsconsist primarily of phenolic compounds and flavonoids. Examples ofdissolved iron are ferric chloride (FeCl₃), ferrous sulfate (FeSO₄), andferric nitrate (Fe(NO₃)₃). Examples of dissolved manganese species aremanganese chloride (MnCl₂) and manganous sulfate (MnSO₄).

This green synthesis pathway using plant reducing agents can replacemilled or solution-based manufacturing of these materials with a greensynthesized process. This process eliminates toxic materials used intraditional production of zero valent metal nanoparticles (i.e., nZVmetals). This process also eliminates toxic materials in waste streamsthat result from the traditional production of NZV metals.

Several sources of dissolved iron can be used to make nZVI using plantextracts. Ferrous sulfate, ferric chloride, and ferric nitrate can allbe used to form nZVI using this green synthesis process. Whereassolutions of each of these salts is a clear liquid, and the plantextracts, e.g., tea extracts, are often light colored liquids, uponcombining the plant extracts with these dissolved iron sources producesa black solution, evidencing the formation of iron nanoparticles.

EXAMPLE 2 Synthesis of Metal Nanoparticles with Plant-Based Surfactantand/or Cosolvent

A methods according to the invention includes the green synthesis ofmetal nanoparticles in the presence of plant-based cosolvents andsurfactants. The plant-based cosolvents and surfactants can serve tostabilize the metal nanoparticles and to minimize their agglomeration,and they can also serve as the reducing agent in the formation of metalnanoparticles. These plant-based cosolvents and surfactants arenaturally derived and can be biodegradable.

Examples of plant-based cosolvents and surfactants that can be used areU.S. FDA Generally Recognized as Safe (GRAS) cosolvents and surfactantsused by VeruTEK for increasing the solubility of LNAPLs and DNAPLsduring oxidation and reduction reactions. Examples of plant-basedcosolvents and surfactants that can be used include VeruSOL™, CitrusBurst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3 (CB-3), andEZ-Mulse, manufactured by Florida Chemical. Any of these can beconsidered a “natural solvent or surfactant” as used herein. CitrusBurst 3 includes a surfactant blend of ethoxylated monoethanolamides ofcoconut oil fatty acids and polyoxyethylene castor oil and d-limonene.Examples of plant-based cosolvents and surfactants that can be usedinclude Alfoterra 53, biodegradable citrus-based solvents, degradablesurfactants derived from natural oils and products, citrus terpene, CASNo. 94266-47-4, citrus peels extract (citrus spp.), citrus extract,Curacao peel extract (Citrus aurantium L.), EINECS No. 304-454-3, FEMANo. 2318, or FEMA No. 2344, terpenes, citrus-derived terpenes, limonene,d-limonene, castor oil, coca oil, coconut oil, soy oil, tallow oil,cotton seed oil, and a naturally occurring plant oil. Examples ofplant-based cosolvents and surfactants that can be used includeALFOTERRA 123-8S, ALFOTERRA 145-8S, ALFOTERRA L167-7S, ETHOX HCO-5,ETHOX HCO-25, ETHOX CO-5, ETHOX CO-40, ETHOX ML-5, ETHAL LA-4, AG-6202,AG-6206, ETHOX CO-36, ETHOX CO-81, ETHOX CO-25, ETHOX TO-16, ETHSORBOXL-20, ETHOX MO-14, S-MAZ 80K, T-MAZ 60 K 60, TERGITOL L-64, DOWFAX 8390,ALFOTERRA L167-4S, ALFOTERRA L123-4S, and ALFOTERRA L145-4S. Forexample, a composition of surfactant and cosolvent can include at leastone citrus terpene and at least one surfactant. Examples of plant-basedcosolvents and surfactants that can be used include nonionic surfactantsethoxylated corn oil, ethoxylated palm oil, ethoxylated soybean oil,ethoxylated castor oil, ethyoxylated coconut oil, ethoxylated coconutfatty acid, ethoxylated coca oil, or amidified, ethoxylated coconutfatty acid. Many of these natural plant oils are US FDA GRAS. Examplesof plant-based cosolvents and surfactants that can be used includeethoxylated castor oil, a polyoxyethylene (20) castor oil, CAS No.61791-12-6, PEG (polyethylene glycol)-10 castor oil, PEG-20 castor oil,PEG-3 castor oil, PEG-40 castor oil, PEG-50 castor oil, PEG-60 castoroil, POE (polyoxyethylene) (10) castor oil, POE(20) castor oil; POE (20)castor oil (ether, ester); POE(3) castor oil, POE(40) castor oil,POE(50) castor oil, POE(60) castor oil, or polyoxyethylene (20) castoroil (ether, ester). Any of these can be considered a “natural solvent orsurfactant” as used herein.

Other examples of plant-based cosolvents and surfactants that can beused include ethoxylated coconut fatty acid, CAS No. 39287-84-8, CAS No.61791-29-5, CAS No. 68921-12-0, CAS No. 8051-46-5, CAS No. 8051-92-1,_(e)thoxylated coconut fatty acid, polyethylene glycol ester of coconutfatty acid, ethoxylated coconut oil acid, polyethylene glycol monoesterof coconut oil fatty acid, ethoxylated coca fatty acid, PEG-15 cocoate,PEG-5 cocoate, PEG-8 cocoate, polyethylene glycol (15) monococoate,polyethylene glycol (5) monococoate, polyethylene glycol 400monococoate, polyethylene glycol monococonut ester, monococonatepolyethylene glycol, monococonut oil fatty acid ester of polyethyleneglycol, polyoxyethylene (15) monococoate, polyoxyethylene (5)monococoate, or polyoxyethylene (8) monococoate. An amidified,ethoxylated coconut fatty acid can include, for example, CAS No.61791-08-0, ethoxylated reaction products of coco fatty acids withethanolamine, PEG-11 cocamide, PEG-20 cocamide, PEG-3 cocamide, PEG-5cocamide, PEG-6 cocamide, PEG-7 cocamide, polyethylene glycol (11)coconut amide, polyethylene glycol (3) coconut amide, polyethyleneglycol (5) coconut amide, polyethylene glycol (7) coconut amide,polyethylene glycol 1000 coconut amide, polyethylene glycol 300 coconutamide, polyoxyethylene (11) coconut amide, polyoxyethylene (20) coconutamide, polyoxyethylene (3) coconut amide, polyoxyethylene (5) coconutamide, polyoxyethylene (6) coconut amide, or polyoxyethylene (7) coconutamide. Any of these can be considered a “natural solvent or surfactant”as used herein.

Other examples of plant-based cosolvents and surfactants that can beused include yucca extract, soapwood extract, and other natural plantsthat produce saponins, such as horse chestnuts (Aesculus), climbing ivy(Hedera), peas (Pisum), cowslip, (Primula), soapbark (Quillaja),soapwort (Saponaria), sugar beet (Beta) and balanites (Balanitesaegyptiaca). Any of these can be considered a “natural solvent orsurfactant” as used herein. Many surfactants derived from natural plantoils are known to exhibit excellent surfactant power, and arebiodegradable and do not degrade into more toxic intermediary compounds.

In addition to stabilizing green synthesized metal nanoparticles, suchas zero valent metal nanoparticles, e.g., nZVI particles, againstagglomeration and serving as the reducing agent in the formation ofmetal nanoparticles, the plant-based cosolvents and surfactants canpromote solubilization of chemicals of concern such as NAPLs, LNAPLs,and DNAPLs. For example, soil and/or water contaminated with NAPLs,LNAPLs, and/or DNAPLs can be treated with a remediation composition thatinclude metal nanoparticles, e.g., zero valent metal nanoparticles, anda plant-based natural solvent or surfactant, in order to remediate thecontaminated soil and/or water by destroying NAPLs, LNAPLs, and/orDNAPLs and decreasing their concentration.

Preparation of metal nanoparticles using green synthesis methodsaccording to some embodiments of the invention has been demonstratedusing a green cosolvent-surfactant system (VeruSOL™-3), a mixture ofU.S. FDA Generally Recognized as Safe (GRAS) citrus and plantextract-based materials. This enables the preparation of metalnanoparticles with a food-grade cosolvent-surfactant system that can beused in the remediation of highly hydrophobic chemicals, non aqueousphase liquids (NAPLs) and hydrophobic chemical or biological agents ormaterials.

Trials were conducted in which nZVI particles were produced using ferricchloride and green tea extract with VeruSOL™ concentrations at 2 g/L, 5g/L, and 10 g/L. A control was prepared using a mixture of ferricchloride and green tea extract alone. The presence of VeruSOL™-3 did notimpact the formation of nZVI particles. The presence of VeruSOL™-3 inthe ingredients of the nZVI particles enables the solubilization anddesorption of hydrophobic organic compounds, such as halogenatedsolvents, PCBs, and pesticides, and subsequent reduction of thesecompounds with nZVI. A further advantage of this new green syntheticprocess for preparing nZVI particles is that it can be carried out usingchelated iron. nZVI particles were made using Fe chelated with ethylenediamine tetraacetic acid (EDTA) and citric acid. Additionally,VeruSOL™-3 was also used in two of the experiments, demonstrating thatthe nZVI particles can be made in the presence of VeruSOL™-3 andchelated iron. Prior work by Feng and Hoag (2004) demonstrated thatchelates can be used to strip iron from hydroxides of iron. Chelates canbe used according to the invention to complex with iron naturallypresent in soils and groundwater, which can then be used to form nZVIparticles.

Nanoscale zero valent iron particles were manufactured in the presenceof a cosolvent-surfactant mixture, ferric chloride, and chelated ironspecies, including Fe(III)-EDTA and Fe(III)-citric acid. TransmissionElectron Microscopy (TEM) images were made of nZVI particles made withvarious concentrations of a cosolvent-surfactant mixture (VeruSOL™-3)ranging in concentration from 0.0 g/L to 10 g/L (FIGS. 14 through 17).These figures demonstrate that as the cosolvent-surfactant concentrationincreased, the agglomeration of particles decreased, with the smallestamount of particle agglomeration occurring at the 10 g/L concentration.Using Fe(III)-EDTA and Fe(III)-citric acid as the dissolved iron sourceto make the nZVI particles led to a significant difference in the sizeof particles versus those made when VeruSOL™-3 cosolvent-surfactant waspresent in solution during nanoparticle preparation (FIGS. 18-21). Onemajor advantage of some compounds, compositions and methods of theinvention is that a chelate may be added to soil to extract iron fromthe soil and/or groundwater, so that this indigenous source of iron maybe used instead of an added iron source.

Chelating compounds other than ethylene diamine tetraacetic acid (EDTA)and citric acid can be used. For example, ethylenediaminedissuccinate(EDDS) can be used. Some examples of chelated iron species that can beused are Fe(III)-EDTA , Fe(III)-citric acid, Fe(III)-EDDS, Fe(II)-EDTA ,Fe(II)-citric acid, and Fe(II)-EDDS.

EXAMPLE 3 Coating of NZVI, NZVMn, and Bimetallic NZVI, NZVMn

The use of nanoparticle zero valent iron (nZVI) and nanoparticle zerovalent manganese (nZVMn) can be limited in environmental applicationsbecause they may exhibit a tendency to aggregate into micron-sizedparticles, thus losing some of their surface area to mass benefit.Additionally, nZVI and nZVMn particles can be highly reactive, and theirsurfaces can become quickly passivated and oxidized. In manyapplications including those for remediation, there is a need for theseparticles to exist and retain reactivity for months or even years.Coating the nZVI and nZVMn particles can reduce the rapid agglomeration,oxidation, and passivation of the nanoscale particles.

In a green approach according to some embodiments of the invention, bulkquantities of nanocomposites containing, for example, transition metalssuch as Cu, Ag, In, and Fe, can be produced at room temperature using abiodegradable polymer such as carboxymethyl cellulose (CMC) by reactingrespective metal salts with the sodium salt of CMC in aqueous media.These nanocomposites exhibit broader decomposition temperatures whencompared with control CMC, and Ag-based CMC nanocomposites exhibit aluminescent property at longer wavelengths. Noble metals such as Au, Pt,and Pd do not react at room temperature with aqueous solutions of CMC,but do so rapidly under microwave irradiation (MW) conditions at 100° C.The nanocomposites obtained at room temperature and microwave conditionswere characterized using scanning electron microscopy, transmissionelectron microscopy, infrared spectroscopy, UV-visible spectroscopy,X-ray mapping, energy-dispersive analysis, and thermogravimetricanalysis. This environmentally benign approach permits the relativelyeasy preparation of noble nanostructures of several shapes, withoutusing any toxic reducing agents, such as sodium borohydride (NaBH₄),hydroxylamine hydrochloride, and others. The approach uses the benignbiodegradable polymer CMC and does not require a separatecapping/surfactant agent. Thus, the approach can produce nanoparticlesfor use in a wide and varied field of technological application, forexample medicinal and land remediation applications.

The green synthesis of zero valent metals and bimetallic species usingplant reducing agents along with biopolymers, with or without VeruTEK'sVeruSOL™ green cosolvents and surfactants, can be used to makehydrophobic organic coated nZVI and nZVMn to enhance solvophobicity(with and without bimetallic metals). The coatings may also exhibitamphiphillic properties because of the presence of surfactant moleculespresent in the composite matrix. The coatings and composite structuresof these nanometal species can also exhibit anionic, cationic, orzwitterionic surface charge properties.

The first and second dissolved metal ions can be added to the vesselmore or less simultaneously, leading to nanoparticles in which the firstand second metals are interspersed throughout the metal nanoparticles.Or the first dissolved metal ion can be added to a vessel first andadding the second dissolved metal ion after a period of time, forexample, of at least about 1 second, 10 seconds, 15 seconds, 30 seconds,or 60 seconds, which generally leads to nanoparticles in which the firstmetal is present primarily in the core of the metal nanoparticle and thesecond metal is present primarily in an outer layer around the core ofthe metal nanoparticle. As used herein, “simultaneously” encompassesevents that happen at precisely the same time as well as events thathappen somewhat asynchronously, provided they are close enough in timeto substantially accomplish the ends of the procedures requiring more orless simultaneous events. For example, in a procedure for preparingbimetallic nanoparticles in which it is desired that the metals beinterspersed throughout the particle, introduction of the two metal ionswill be considered “simultaneous” if, for example, the procedureproduces, or is capable of producing, bimetallic nanoparticles with themetals substantially interspersed throughout the particles.

Bimetallic Fe/Pd nanoparticles can be prepared as follows: prepare 20g/L green tea extract by adding 20 grams of green tea to 1 liter ofdeionized water and bring to 80° C. Let tea cool to room temperature andvacuum filter through 90 mm glass fiber filter. Prepare 0.1 M FeCl₃ bydissolving 16.2 g of solid FeCl₃ in 1 L of deionized water. Preparepalladium chloride solution in deionized water at appropriateconcentration, 0.2 M in this study. Green tea synthesized nano-scalezero valent iron (GT-nZVI) is then prepared by adding 0.1 M of FeCl₃ tothe 20 g/L filtered green tea in a 2:1 volume ratio, resulting in a 66mM Fe concentration in the final GT-nZVI solution. Add appropriateamount of PdCl₂ to GT-nZVI solution within 30-60 seconds after FeCl₃ isadded to the green tea. Shake. This and/or similar methods can also beused to prepare nanoparticles comprising other metals, as well asparticles comprising more than two metals.

EXAMPLE 4 Trial Production of nZVI Particles With Green Tea Extract andFerric Chloride in the Presence of Carboxy Methyl Cellulose (CMC),VeruSOL-3™, and/or Trichloroethylene (TCE)

A series of batch tests were conducted to evaluate the capability of thegreen synthesis of nZVI using green tea extract and ferric chloride withthe following: a) carboxy methyl cellulose (CMC); b) VeruSOL™-3; and c)trichloroethylene (TCE). Testing conditions are shown in Table 2.

TABLE 2 Compatibility of Carboxy Methyl Cellulose, VeruSOL ™-3 andTrichloroethylene with Green Tea & Ferric Chloride Synthesized NanoscaleZero Valent Iron CMC Satu- VS-3 Pure Green Dyed rated Water (10 g/L)VS-3 FeCl3 Tea-Extract Pure TCE Test mL mL mL mL mL mL I-1 20 20 I-2 420 I-3 20 20 I-4 4 20 I-5 20 20 I-6 4 20 I-7 40 1 I-8 4 24 12 1 I-9 4 2412 I-10 4 0.4 24 12 1 I-11 4 0.4 24 12 I-12 0.4 24 12 Notes: 1)Reagants- Carboxy methyl cellulose (CMC) Saturated Water, VeruSOL ™-3,FeCl₃, Green Tea Extract, Dyed Pure TCE 2) Tests Conducted in 40 mLvials 3) Interfacial Tension and photographs taken 24 hours after a 1minute initial mixing period 4) Concentrations of VeruSOL ™-3 usedresults in 10 g/L concentration in vial 5) 0.1M ferric chloride used intest 6) Carboxy methyl cellulose used a from a saturated solution (~3%)of sodium carboxy methyl cellulose (MW-90,000)

In Test Vials I-1 and I-2, the compatibility of carboxy methyl cellulosewith VeruSOL™-3 was evaluated at two CMC concentrations. In both casesthere were no separate phases detected when CMC and VeruSOL™-3 weremixed together. In Test Vials I-2 and I-3, the ability of carboxy methylcellulose to chelate the iron in ferric chloride was evaluated. When 4mL of a saturated CMC solution was added to 0.1 N ferric chloride,precipitation of iron was observed for Test Vial I-4. However, when 20mL of a saturated CMC solution was added to 0.1 N ferric chloride, therewas no precipitation and the ferric chloride was fully chelated. In TestVials I-5 and I-6, the compatibility of CMC and green tea extract wereevaluated to determine if there would be separate phase reactionproducts. Both of these solutions indicated no separate phase. In TestVial I-7, the compatibility of CMC with pure phase trichloroethylene wasevaluated. Visual observation revealed no apparent reactivity of TCEwith CMC. In Test Vials I-8 and I-9, the synthesis of nZVI using ferricchloride and green tea extract was evaluated in the presence of CMC(I-9) and in the presence of CMC and pure phase TCE (I-8). There was noapparent impact on the ability to form nZVI particles when CMC and CMCplus TCE were present. Test vials clearly exhibited a layer of TCE underthe settled nZVI.

In Test Vial 10, the synthesis of nZVI using ferric chloride and greentea was evaluated in the presence of CMC, TCE, and VeruSOL™-3. Theappearance of this test was similar to Test Vial I-8 (similar conditionsto Test Vial I-10 but without TCE); however, the TCE appeared to attachto the glass walls of the Test Vial. In Test Vials I-11 and I-12, theeffects were determined on the addition of VeruSOL™-3 on the synthesisof nZVI using ferric chloride and green tea extract in the presence ofCMC (Vial I-11) and absence of CMC (Vial I-12). In both cases theaddition of VeruSOL™-3 stabilized the nZVI and inhibited much of theagglomeration and settling observed when VeruSOL™-3 was not added duringthe synthesis of nZVI using ferric chloride and green tea extract.

Hoag and Collins (Patent pending; U.S. Ser. No. 12/068,653) teach thatVeruSOL™-3, a mixture of d-limonene and nonionic surfactants consistingof ethoxylated plant oils, can be used to dissolve a variety of organicliquids, including TCE. The test results clearly indicate that nZVI canbe synthesized using ferric chloride and green tea extract in thepresence of TCE without any impact on particle formation. Therefore,nZVI can be made using this green synthesis process in the presence ofVeruTEK's VeruSOL™-3 to enable controlled dissolution of Non AqueousPhase Liquids (NAPL). Additionally, since nZVI can be made in situ, asdemonstrated in the soil column test results, nZVI can also bemanufactured in situ in the presence of pure phase TCE.

EXAMPLE 5 In Situ Formation of Metal Nanoparticles

A method according to the invention was used to produce nanoscale zerovalent iron particles (nZVI) in soil columns, as a simulation of in situformation of nanoscale iron particles in soil. Two column experimentswere conducted to evaluate the potential for in situ generation of nZVIusing Fe(NO₃)₃ and either green tea extract or lemon balm extract. Twostock solutions were each injected in an upflow mode into soil columnspacked with ASTM 20/30 sand with the dimension of 300 cm long by 30 cmdiameter. For Column 2, green tea extract and 0.1 M Fe(NO₃)₃ were eachsimultaneously injected at flowrates each at 0.15 mL/min for a totalinjected flowrate of 0.30 mL/min.

The green tea extract was made as follows: 200 mL of deionized waterwere heated in a beaker to a temperature of 82° C. and 4.01 grams ofChunmee green tea was added. The beaker was covered with aluminum foiland the tea was heated in the water for 5 minutes. After 5 minutes, thebeaker was removed from the heat and the tea was allowed to settle for 1hour and return to 25° C. The tea extract supernatant was then removedfrom the beaker and either immediately used or stored at 4° C. for lateruse. The Lemon Balm Extract was made using a similar procedure.

The initial formation of nZVI in the bottom (inlet) of the soil columnwas observed in the bottom of Column 2, as black in an otherwiselight-colored liquid. Effluent from Column 2 was collected and sampledfor electrolytic conductivity and was visually observed. Sample number 4was collected between effluent volumes of from 117 mL to 150 mL in a 40mL sample vial and represented approximately 0.56 pore volumes of flowthrough the column. Sample number 5 was collected between effluentvolume from 150 mL to 200 mL in a 60 mL sample vial and representedapproximately 0.74 pore volumes of flow through the column. Samplenumber 6 was collected between effluent volumes of from 200 mL to 259 mLin a 60 mL sample vial and represented approximately 0.96 pore volumesof flow through the column. The electrolytic conductivity values forSamples 4, 5, and 6 were 0.86 mS/cm, 2.27 mS/cm, and 17.4 mS/cm,respectively. An examination of the effluent samples demonstrated thatthe nZVI began eluting from the column between Samples 4 and 5. Acomparison of the Lemon Balm Extract and 0.1 M Fe(NO₃)₃ Column(Column 1) to a control column (no Lemon Balm Extract or ferric nitrate)clearly showed the accumulation of nZVI in the column, but the nZVIcontinued to elute from the column as long as the test runs wereconducted. The electrolytic conductivity of the Column 1 (Lemon BalmExtract and 0.1 M Fe(NO₃)₃) effluent is shown in FIG. 1. It is evidentthat the nZVI eluted from the column and continued to elute afterbreakthrough. The same trend is evident in Column 2 (Green Tea Extractand 0.1 M Fe(NO₃)₃), as is shown in FIG. 2.

EXAMPLE 6 DPPH Stable Radical Method For Screening of Plant Extracts ForUse in Synthesis of Metal Nanoparticles

A 2,2-diphenyl-1-picrylhydrazyl (DPPH) stable radical method foranalysis of radical scavenging properties related to antioxidantactivity was used to screen plant extract for potential use in themanufacture of zero valent nanoparticles. This method was used todetermine and optimize the amount of ferric iron added to a given plantextract for the formation of zero valent nanoparticles. One optimizationgoal in the manufacture of nanometal particles using plant extracts isto determine how much ferric iron (or other metal) can be added to agiven plant extract to ensure complete conversion of ferric iron to zerovalent iron. This DPPH screening method also can be used with metalsother than iron and with plant extracts other than green tea for themanufacture of nanometals using plant extracts.

The experimental design is presented in Table 3.

TABLE 3 DPPH Stable Radical Consumption by Plant Extracts Before andAfter Reaction with Ferric Chloride to Manufacture Nanoscale Zero ValentIron Particles Absorbance of Treated Samples at Test Test ReactionMatrix 517 nm Observations Conc, g/L 1 L mL DI Water + 3 mL EtOH + 1 mL0.955 Purple DPPH Soln 2 1 mL 200x, 2.5 g/L Tea Extract + 3 mL 0.836Purple 2.5 EtOH4 + 1 mL DPPH Soln 3 1 mL 200x, 5 g/L Tea Extract + 3 mL0.793 Purple 5 EtOH4 + 1 mL DPPH Soln 4 1 mL 200x, 10 g/L Tea Extract +3 mL 0.637 Purple 10 EtOH4 + 1 mL DPPH Soln 5 I mL 200x, 20gfL TeaExtmct + 3 mL 0.593 Light Purple 20 EtOH4 + 1 mL DPPH Soln 6 1 mL 200x,40 g/L Tea Extract + 3 mL 0.072 Tea 40 EtOH4 + 1 mL DPPH Soln 7 1 mL200x, 2.5 g/L Tea Extract/NZV1 + 0.86 Purple 2.5 3 mL EtOH4 + 1 mL DPPHSoln 8 1 mL 200x, 5 g/L Tea Extract/NZVI + 0.858 Purple 5 3 mL EtOH4 + 1mL DPPH Soln 9 1 mL 200x, 10 g/L Tea Extract/NZVI + 0.802 Purple 10 3 mLEtOH4 + 1 mL DPPH Soln 10 1 mL 200x, 20 g/L Tea Extract/NZVI + 0.774Purple 20 3 mL EtOH4 + 1 mL DPPH Soln 11 1 mL 200x, 40 g/L TeaExttact/NZVI + 0.527 Purple pink 40 3 mL EtOH4 + 1 mL DPPH SolnExperimental Procedure: 1) DPPH (500 uM) was dissolved in pure ethanol(96%). The radical stock solution was prepared fresh daily. 2) The DPPHsolution (1 mL)was added to 1 mL of sample extract with 3 mL of ethanol.3) The mixture was shaken vigorously for 10 min and allowed to stand atroom temperature in the dark for another 20 min. 4) A decrease inabsorbance of the resulting solution (the result of consumption of theradical scavenger) was measured at 517 nm.

Tests 1 though 5 in Table 2 were used to determine the effects ofincreasing concentrations of dry green tea used to make tea extract inheated water on the spectroscopic absorbance of the DPPH radical. Theresults of tests 1 through 5 are represented by the lower line of bestfit in FIG. 13, demonstrating a linear relationship between dry greentea concentration (used to make the tea extract) and DPPH absorbance at517 run. The green tea extract was diluted by a factor of 200 to obtainusable absorbance measurements in a linear range. The same green teaextracts used in tests 1 through 5 were then added to ferric chloride tomake zero valent iron nanoparticles. A ratio of 2:1 (v/v) of 0.1M FeCl₃to tea extract was used to make the zero valent iron nanoparticles usedin tests 7 through 11. The DPPH absorbance of the solution following theformation of nZVI particles was considerably higher than with theoriginal green tea extracts alone, reflecting that some of the compoundsin the tea extract responsible for consumption of the DPPH free radicalwere consumed in the formation of the nZVI particles. This is evident byexamination of the upper line of best fit in FIG. 13. The differencebetween the two lines represents the net consumption of DPPH freeradical absorbance when nanometal particles are manufactured.Polyphenolic compounds and other compounds in the tea extract areconsumed during the production of metal nanoparticles, as evidenced bythe difference between the two lines. The net consumption can be used torun successive dosing tests for the concentration ratio of the metalsalt solutions and the plant extract, thereby enabling a relationship tobe derived between DDPH absorption and metal salt added. Thisrelationship can be used to establish the optimum dose of plant extractand metal salt solution to use the plant extract to the maximum extentin the formation of metal nanoparticles.

EXAMPLE 7 Green Synthesis Manufacture of Noble Metal Nanoparticles atRoom Temperature

A method according to some embodiments of the invention represents agreen approach that generates bulk quantities of nanocrystals of noblemetal, such as silver (Ag) and palladium (Pd), using a plant extract,such as coffee and tea extract, at room temperature. This single-potmethod uses no surfactant, capping agent, and/or template. The obtainednanoparticles have a diameter size of from about 20 nm to about 60 nmand are crystallized in face centered cubic symmetry. The method may beused to produce nanoparticles of other metals, such as other noblemetals, e.g., gold (Au) and platinum (Pt).

To produce the coffee extract, 400 mg of coffee powder (Tata Bru coffeepowder 99%) was dissolved in 50 mL of water. 2 ml of 0.1 N AgNO₃ (AgNO₃,Aldrich, 99%) was mixed with 10 ml of the coffee extract and shaken toensure thorough mixing. The reaction mixture was allowed to settle atroom temperature.

2 ml of 0.1 N PdCl₂ (PdCl2, Aldrich, 99%) was mixed with 10 ml of thecoffee extract and shaken to ensure thorough mixing. The reactionmixture was allowed to settle at room temperature.

To produce the tea extract, 1 gm of tea powder (Red label from Tata,India Ltd. 99%) was boiled in 50 ml of water and filtered through a 25μm Teflon filter. 2 ml of 0.1 N AgNO₃ (AgNO₃, Aldrich, 99%) was mixedwith 10 ml of the tea extract and shaken to ensure thorough mixing. Thereaction mixture was allowed to settle at room temperature.

2 ml of 0.1 N PdCl₂ (PdCl₂, Aldrich, 99%) was mixed with 10 ml of thetea extract and shaken to ensure thorough mixing. The reaction mixturewas allowed to settle at room temperature.

To evaluate the effect of the source of the coffee or tea extract on themorphology of the Ag and Pd nanoparticles prepared, several experimentssimilar to those described above were carried out with coffee and teaextracts from various sources. The results are shown in Table 4.

TABLE 4 Various brands of tea/coffee used to generate nanoparticles.Item Brand Names Shape Size 1 Sanka ™ coffee faceted ~100 nm 2 Bigelow ™tea spherical ~20 nm 3 Luzianne ™ tea spherical ~100 nm 4 Starbucks ™coffee spherical ~10 nm 5 Folgers ™ coffee spherical ~10 nm 6 Lipton ™tea spherical ~20-30 nm

0.1 mL of the products containing nanoparticles was dispersed with 5 mLdistilled water to prepare samples for transmission electron microscopy(TEM) and scanning electron microscopy (SEM) analysis. TEM grids wereprepared by placing 1 μL of the particle solution on a carbon-coatedcopper grid and drying at room temperature, and UV-visible spectrummeasurements were taken. To obtain better SEM images, the product wasdrop-cast on carbon tape and allowed to dry; a thin layer of gold wascoated on the surface to make it conducting. TEM was performed with aJEOL-1200 EX microscope operated at 120 kV. SEM was carried out with afield-emission microscope (Leo, 1530 VP) operated at an acceleratingvoltage of 20 kV. X-ray diffraction (XRD) patterns were obtained from aScintag X-ray diffractometer at a 2 theta range of 2-600 using CuKαradiation. Open-circuit voltage potentials were obtained using 1 M NaClwith reference to saturated calomel electrode (SCE).

Various shapes and sizes for Ag and Pd nanoparticles using coffee andtea extract were observed. Drop-coated films of Ag and Pd nanoparticleswere prepared by room temperature aqueous solution evaporation oncarbon-coated copper grids and analyzed by TEM (FIG. 3 a-d). At lowmagnification, a number of highly polydisperse Ag nanoparticlespossessing a variety of shapes were observed (FIG. 3 a). The TEM imageshows that Ag nanoparticles were well-separated from each other with anapparently uniform inter-particle separation. This indicates that the Agnanoparticles were capped by organic molecules, such as caffeine, and athigher magnifications it can be seen clearly (FIG. 3 b). In the case ofPd nanoparticles, the sizes seemed to be smaller than Ag nanoparticlesand the inter-particle distance was uniformly separated and well aligned(FIG. 3 c-d).

The particles sizes ranged from about 20 nm to about 60 nm, and theparticles were well-separated from each other. The polyphenols acted asa reducing agent as well as a capping agent. The control experimentscarried out with pure catechin yielded tennis-ball-like structures forAu and Ag (FIG. 3 and FIG. 11). However, pure caffeine yielded wire-likestructures for Au (FIG. 12) and reaction with AgNO₃ is very slow withless yield. This approach was carried out for nanoparticles producedwith coffee and tea from various sources (Table 4), and correspondingTEM images are shown in FIGS. 4 and 5. The Ag and Pd nanoparticles weremostly spherical and had sizes ranging from as low as about 5 nm toabout 100 nm, depending upon the source of coffee or tea extract used(see FIG. 4 and FIG. 5).

The control experiments carried out with pure catechin showedspherical-ball-like structures for Ag and Pd, as shown in FIG. 6.

The formation mechanism of Ag and Pd was studied using UV spectroscopy,which was found to be a useful technique for the analysis ofnanoparticle formation over time. As illustrated in FIG. 7, a surfaceplasmon peak located at ˜460 nm was observed for the Ag nanoparticlesafter 2 hours of reaction (curve (f) prepared from tea extract. A strongabsorption peak was observed at ˜340 nm corresponding to the absorptionof polyphenol compounds present in the tea.

The UV spectra of Ag and Pd nanoparticles prepared from coffee and teaextracts are shown in FIG. 8. The generation of strong but broad-surfaceplasmon peaks has been observed in the case of various metalnanoparticles over a wide range of particle sizes, e.g., from about 200to about 1200 nm.

The reduction potential of caffeine is ˜0.3 V vs. SCE (see FIG. 9) whichis sufficient to reduce metals viz. Pd (reduction potential 0.915 V vs.SCE), Ag (reduction potential 0.80 V vs. SCE), and also for reducingAu⁺³ to Au⁰ (reduction potential is 1.50 V vs. SCE) and Pt (reductionpotential 1.20 V vs. SCE). The formation of Ag and Pd nanoparticles withcaffeine is understood to take place via the following steps:

complexation with Ag and Pd metal salts

simultaneous reduction of Ag and Pd metal and formation of capping withoxidized caffeine.

FIG. 10 a-d shows the XRD patterns of Ag and Pd nanoparticles obtainedfrom coffee and tea extract, respectively, from an aqueous solution dropcoated film on glass plate. From the XRD patterns, prominent Braggreflections at 28 values of 38.3 and 42.6 were observed which correspondto the (111) and (200) Bragg reflections of face centered cubic (fcc) Agnanoparticles (FIG. 10 a-b). See, e.g., Y. Sun and Y. Xia, Science,2002, 298, 2176. However, in the case of Pd nanoparticles, layeredstructures of caffeine remained with a well-developed progression ofintense reflections, which are successive orders of diffraction with alarge d spacing (see FIG. 10 c-d). See, L. M. Juliano and R. R.Griffiths, Psychopharmacology, 2004, 176, 1. The diffraction patternscan be interpreted to depict a crystal structure in which Pd andcaffeine molecules occur in regularly stacked layers with a largeinterlayer lattice dimension, and relatively small distances in theinterlayer two-dimensional lattice. The presence of narrow interlayerreflections indicates that there is crystallographic registry of layers.

EXAMPLE 8 Green Synthesis of Nanoscale Bimetallic Zero Valent Metals

Methods according to the invention, similar to those described above,can be used to manufacture bimetallic nZV materials. For example,bimetallic metal nZV materials can be made by adding additional metalsalts to the base metal salt used. In the case of nZV iron, palladium,nickel, silver, and other metals can be used to develop bimetallicnanoparticles. The uses of these materials can be substantially similarto those described above. The methods described herein can also be usedto prepare nZV particles comprising three or more metals, as would beappreciated by a person of ordinary skill in the art.

The preparation of bimetallic nanoparticles from metal salts isgenerally carried out using one of two methods: 1) co-reduction and 2)successive reduction of two metal salts. Successive reduction can becarried out to prepare core-shell structured bimetallic nanoparticles.Co-reduction is the simpler preparative method for bimetallicnanoparticles. In this process, first the metal ions coordinate withgreen tea/coffee extract, and then reduction occurs. Addition of asecond metal salt and subsequent reduction with excess stabilizing greentea/coffee extract results in the formation of core-shell structure. Theformation of core-shell structure will depend upon the metal salts usedand the reducing/stabilizing agent used in the preparation.

The plant extracts according to the invention may be aqueous plantextracts from a wide variety of plant materials, obtained in water fromcold to boiling temperatures, with or without mild surfactants and withor without cosolvents, e.g., ethanol or d-limonene, to facilitateextraction. The extracts may be crude, or may be further purified, aswith catechins. The extracts generally exhibit high anti-oxidant and/orpolyphenol concentrations sufficient to form nanoparticles of metalaccording to the invention.

EXAMPLE 9 Degradation of Bromothymol Blue by “Greener” Nano-ScaleZerovalent Iron Synthesized Using Tea Polyphenols

The focus of this study is to compare the degradation of bromothymolblue, a model contaminant, by green tea synthesized nano-scale zerovalent iron (GT-nZVI), Fe-EDTA (Fe-ethylenediamine tetraacetate), andFe-EDDS (Fe-(S,S)-ethylene diamine-N,N′)-disuccinic Acid) catalyzedhydrogen peroxide. The degradation of the model contaminant ismonitored, allowing for the determination of rate constants at variousconcentrations of iron. The following green single-step synthesis ofiron nanoparticles using tea (Camellia sinensis) polyphenols uses noadditional surfactants/polymers as capping or reducing agents. The teaextract (polyphenols) used in this study functions both as a reducingand capping agent for Fe. It has additional advantages due to its highwater solubility, low toxicity, and biodegradability. The reactionbetween polyphenols and ferric nitrate occurs within a few minutes atroom temperature, as indicated by color changes from pale yellow to darkgreenish/black in the formation of iron nanoparticles.

Bromothymol blue, a commonly deployed pH indicator, is used here as amodel contaminant for free radical reactions, due to its stability inthe presence of H₂O₂ and its absorbance in the visible range at pH 6.The concentration of bromothymol blue is conveniently monitored usingultraviolet-visible (UV-Vis) spectroscopy during treatment withiron-catalyzed H₂O₂. Various concentrations of iron are tested to allowfor the determination of initial rate constants for the different ironsources.

This new synthetic method is an extremely simple green approach thatgenerates bulk quantities of relatively stable nanocrystals of iron (Fe)using tea extract at room temperature.

Green tea extract was prepared by heating 20 g/L green tea to 80° C.followed by vacuum filtration. A solution of 0.1M FeCl₃ was prepared bydissolving 16.2 g of solid FeCl₃ (Acros Organics) in 1 L of deionizedwater. Green tea synthesized nano-scale zero valent iron (GT-nZVI) wasthen prepared by adding 0.1 M FeCl₃ to 20 g/L green tea in a 2:1 volumeratio, resulting in a 66 mM Fe concentration in the final GT-nZVIsolution.

Solutions of Fe-EDTA and Fe-EDDS were prepared at 350 mg/L as iron.Fe-EDTA was prepared by dissolving 0.2378 g of ethylenediaminetetraacetate (EDTA) (Fisher) in deionized water followed by 0.1737 g ofFeSO₄ (Fisher). H₂SO₄ was then added to the solution, drop-wise, untilit turned a pale green color. The solution was then brought to a totalvolume of 100 mL with deionized water. Fe-EDDS was prepared in the samemanner using 0.2239 g of (S,S)-ethylene diamine-N,N′-disuccinic Acid(EDDS) and 0.1737 g of FeSO₄. An unstabilized 30% H₂O₂ solution wasobtained from Fisher. A 500 ppm bromothymol blue solution was preparedby dissolving 50 mg bromothymol blue (Aldrich) in 100 mL of deionizedwater.

The reaction vessel used for all experiments was a quartz cuvette.Ultraviolet-visible absorbance measurements were made throughout theexperiment with a photodiode array scanning spectrophotometer (Beckman).Three iron sources were tested at various concentrations as a catalystfor the formation of H₂O₂ free radicals: GT-nZVI, Fe-EDTA, and Fe-EDDS.Before each trial, a blank was read which included 3 mL deionized waterwith the appropriate iron source and concentration. A clean cuvette wasthen loaded with 3 mL of 500 ppm bromothymol blue and H₂O₂ was added.With the cuvette in the spectrophotometer, the iron source was added tothe solution and quickly mixed with the pipette. Scans were startedimmediately after the injection of the iron source and the solution wasleft untouched until completion.

The first series of experiments examined the degradation of bromothymolblue with GT-nZVI catalyzed H₂O₂ at various nano-scale ironconcentrations. The second and third series of experiments examined thedegradation of bromothymol blue with Fe-EDTA catalyzed H₂O₂ and Fe-EDDScatalyzed H₂O₂, respectively. A 2% H₂O₂ concentration was used for allexperiments. Experiments were conducted using GT-nZVI concentrations at0.03 mM, 0.06 mM, 0.12 mM, and 0.33 mM as Fe. Similarly, experimentsusing. Fe-EDTA and Fe-EDDS had concentrations at 0.12 mM, 0.33 mM, and0.5 mM; an additional concentration of 0.66 mM as Fe was also used forFe-EDDS.

The reduction potential of caffeine is 0.3 V vs. SCE which is sufficientto reduce metals viz. Fe (reduction potential −0.44 V vs. SCE). Theformation of Fe nanoparticles with caffeine/polyphenols is understood tooccur via the following steps: (1) complexation with Fe salts, (2)simultaneous reduction of Fe (+III) capping with oxidizedpolyphenols/caffeine. The reduction of Fe was confirmed using UV spectraand is shown in FIG. 22. The blank extract has an absorption beginningat 500 nm which is similar to the control Fe(NO₃)₃ solutions. Thereaction between Fe(NO₃)₃ and tea extract was instantaneous and thecolor of the reaction mixture changed from yellow to dark brown as shownin the inset of FIG. 22. This general approach was explored using othercommon salts of iron as the source of dissolved Fe, namely FeCl₃, FeSO₄,and FeEDTA. A variety of additional plant sources of polphenols havealso been used including several herbs including lemon balm (Melissaofficinalis), and parsley (Crispum crispum) and grains, for examplesorghum bran (Sorghum spp.). After the reaction, the UV spectra hadbroad absorption at a higher wavelength and there was no sharpabsorption at lower wavelengths as occurred in the controls.Representative XRD pattern of the iron nanoparticles is shown in FIG. 23and the pattern was compared with JCPDS pattern 00-050-1275. The highestintensity plane (102) is well-matched with the reported pattern.However, other additional reflections were very weak, possibly due topreferred orientation of the iron nanoparticles. Some small additionalpeaks were noted, which may correspond to impurities originating fromthe tea extract.

These iron nanoparticles were tested as a catalyst for the oxidation ofbromothymol blue. The bromothymol has an absorption in the visibleregion which is concentration-dependent (see FIGS. 24 and 33).

Initial bromothymol blue concentration was 500 mg/L and with 2% hydrogenperoxide, bromothymol blue did not undergo any degradationkatalysis,confirming the lack of a direct oxidation pathway by peroxide. A similarbromothymol blue concentration was tested using different ironconcentrations for peroxide catalysis and is shown in FIGS. 25 and 26.The maximum absorbance, at 431 nm, is at time zero and decreases withevery scan over time, demonstrating the free radical oxidation ofbromothymol blue. Higher iron concentrations accelerated the degradationof bromothymol blue.

The changes in the concentration of the bromothymol blue (pH 6) atdifferent time intervals is illustrated in FIG. 27. Graphs (a) through(e) represent GT-nZVI concentrations in 2% hydrogen peroxide, as setforth in Table 5. The time series graphs demonstrate how bromothymolblue degrades over time in the presence of 2% H₂O₂ and 0.03, 0.06, 0.12and 0.33 mM GT-nZVI respectively. Experimental rate constants ofbromothymol blue oxidation are obtained by monitoring the change inabsorbance at 431.

The fastest degradation of bromothymol blue by catalyzed H₂O₂ occurredwith Fe GT-nZVI at a concentration of 0.33 mM. A linear relationship isdetermined between the natural log of bromothymol blue concentration(In[BTB]) and time, indicating a first order reaction with respect tobromothymol blue concentration, as shown in FIG. 28. The rate constantsincrease between 0.0062 min⁻¹ at 0.03 mM GT-nZVI, to 0.1448 min⁻¹ at0.33 mM GT-nZVI (Table 5).

TABLE 5 Initial rates of decomposition of bromothymol blue with GT-nZVIcatalyzed H₂O₂. Graph GT-nZVI (mM as Fe) Rate (min⁻¹) R² (a) 0 −0.00110.4376 (b) 0.03 0.0062 0.9842 (c) 0.06 0.0152 0.9859 (d) 0.12 0.04490.9938 (e) 0.33 0.1448 0.9925

FIG. 29 illustrates the linear relationship between the initial rateconstants and GT-nZVI concentrations. The highly linear relationship ofthe initial bromothymol blue oxidative rate constants (R²=0.9989) for a2% hydrogen peroxide concentration over a range of Fe concentrations(0.03 mM to 0.33 mM) demonstrates the activity of these heterogeneouscatalysts, with initial rate constants varying from 0.0062 to 0.1448⁻¹.

The degradation of bromothymol blue over time with Fe-EDTA and Fe-EDDScatalyzed 2% H₂O₂, at four different Fe concentrations is shown in FIG.30. FIG. 30 presents the degradation of bromothymol blue concentrationover time with Fe-EDTA (graph (a)) and Fe-EDDS (graph (b)) catalyzedH₂O₂. (a) bromothymol blue treated with 0.12 mM Fe catalyzed HP (2%),(b) bromothymol blue treated with 0.33 mM as Fe catalyzed HP (2%), (c)brornothymol blue treated with 0.50 mM as Fe catalyzed HP (2%), (d)bromothymol blue treated with 0.66 mM as Fe (Fe-EDDS only) catalyzed HP(2%).

Initial rate constants for these reactions were obtained by plottingIn[BTB] as a function of Fe-EDTA or -EDDS concentrations (as Fe). Overthe range of Fe concentrations tested, the results suggest a decrease inthe rate of bromothymol blue degradation with increasing amounts of Fe,as shown in FIG. 31. Because EDTA and EDDS have the ability to stabilizeH₂O₂, increasing concentrations of Fe-EDTA or -EDDS result in anincrease in the stabilization of H₂O₂. This increase in H₂O₂stabilization slows the decomposition of H₂O₂ and the production ofhydroxyl radicals, ultimately slowing the oxidation of bromothymol blue(Tables 6 and 7).

TABLE 6 Initial rates of decomposition of bromothymol blue with Fe-EDTA.Sl No. Fe-EDTA (mM as Fe) Rate (min⁻¹) R² (a) 0.12 0.041 0.96 (b) 0.330.0038 0.9104 (c) 0.5 0.0035 0.9502

TABLE 7 Initial rates of decomposition of bromothymol blue Fe-EDDScatalyzed H₂O₂. Sl No. Fe-EDDS (mM as Fe) Rate (min⁻¹) R² (a) 0.120.0146 0.9742 (b) 0.33 0.0148 0.9375 (c) 0.5 0.0097 0.9936 (d) 0.660.0103 0.9502

FIG. 32 shows the relationship between initial rate constants and theconcentration (as Fe) of Fe-EDTA and Fe-EDDS. Initial rate constants forthe Fe-EDTA catalyzed peroxide varied from 0.0035 to 0.0041 min⁻¹ andFe-EDDS initial rate constants varied from 0.0097 to 0.0148 min⁻¹. It isapparent that the initial rate constants for the oxidation of thebromothymol blue were much greater with the GT-nZVI catalyst than withFe-EDTA or Fe-EDDS. At a Fe concentration of 0.33 mM and a hydrogenperoxide concentration of 0.33 mM, the initial rate constants forbromothymol blue oxidation were 0.1447, 0.0038 and 0.0148 for thecatalysts GT-nZVI, FeEDTA and FeEDDS, respectively. The comparative rateconstants for bromothymol blue oxidation using a GT-nZVI catalyst weremore than an order of magnitude greater than with Fe-EDTA and Fe-EDDS.

EXAMPLE 10 Green Synthesis of Au Nanostructures at Room TemperatureUsing Biodegradable Plant Surfactants

The following describes a convenient one-step room-temperature greensynthesis of gold (Au) nanostructures with different morphologies andsizes (i.e., spheres, prisms, and hexagonal structures), which arereadily prepared from inexpensive starting materials includingplant-based naturally-occurring biodegradable surfactants and cosolventsin water without using any additional capping or reducing reagent. Thesizes vary from nanometer to micron scale level depending on the plantextract used for the preparation. This synthesis concept can enable thefine-tuning of material responses to magnetic, electrical, optical, andmechanical stimuli.

Chloroauric acid tetrahydrate (HAuCl₄.4H2O) and methyl ammonium bromidewas obtained from Aldrich chemical company. Plant extract were obtainedfrom VeruTEK™ Technologies, Inc. of Bloomfield, Conn. VeruSOL-3™ is amixture of d-limonene and plant-based surfactants. VeruSOL-10™,VeruSOL-11™ and VeruSOL-12™ are individual plant-based surfactantsderived from coconut and castor oils. All of the chemicals wereanalytical grade and used without further purification. Doubly distilledwater was used throughout the experiments.

Different concentrations of HAuCl₄ solutions were added to the solutionof plant extracts at room temperature. This mixture was gently mixed,followed by rapid inversion mixing for 2 minutes. The composition of thereaction mixtures are shown in Table 8. Samples for UV spectroscopymeasurements were reaction mixtures dispersed in distilled water. Toobtain better SEM images, the product was drop-casted on carbon tape andallowed to dry. Transmission electron microscopy (TEM) was performedwith a JEOL-1200 EX II microscope operated at 120 kV. Scanning electronmicroscopy (SEM) was carried out with a field-emission microscope (JEOL8400 LV) operated at an accelerating voltage of 20 kV. PanalyticalX-pert diffractometer with a copper Ka source was used to identifycrystalline phases of the lead precipitates. The tube was operated at 45kV and 40 mA for the analyses. Scans were performed over a 2-thetaranging from 5 to 70° with a step of 0.02° and a one-second count timeat each step. Pattern analysis was performed by following ASTMprocedures using the computer software Jade (Versions 8, Materials Data,Inc.), with reference to the 1995-2002 ICDD PDF-2 data files(International Center for Diffraction Data, Newtown Square, Pa.). UVspectra were recorded using Varian UV-visible spectrometer (Model Cary50 Conc).

TABLE 8 Different compositions of reaction mixture Entry CompositionCode 1 VeruSOL-3 ™ 2 mL + 4 mL HAuCl₄ Au-1 2 D-limonene 2 mL + 4 mLHAuCl₄ Au-2 3 VeruSOL-12 ™ 2 mL + 4 mL HAuCl₄ Au-3 4 VeruSOL-10 ™ 2 mL +4 mL HAuCl₄ Au-4 5 VeruSOL-11 ™ 2 mL + 4 mL HAuCl₄ Au-5 6 VeruSOL-3 ™ 2mL + 4 mL HAuCl₄ + 10 H₂O Au-6 7 D-limonene 2 mL + 4 mL HAuCl₄ + 10 H₂OAu-7 8 VeruSOL-12 ™ + 4 mL HAuCl₄ + 10 H₂O Au-8 9 VeruSOL-10 ™ + 4 mLHAuCl₄ + 10 H₂O Au-9 10 VeruSOL-11 ™ + 4 mL HAuCl₄ + 10 H₂O Au-10 11VeruSOL-3 ™ 1 mL + 10 mL HAuCl₄ Au-11 12 D-limonene 1 mL + 10 mL HAuCl₄Au-12 13 VeruSOL-12 ™ 1 mL + 10 mL HAuCl₄ Au-13 14 VeruSOL-10 ™ 1 mL +10 mL HAuCl₄ Au-14 15 VeruSOL-11 ™ 1 mL + 10 mL HAuCl₄ Au-15

Formation of gold nanostructures was achieved at room temperature,followed by the in situ measurement by the UV-vis spectra. The reactionsolution containing plant extracts obtained from VeruTEK Technologies,Inc. of Bloomfield, Conn. HAuCl₄4H₂O was introduced into a quartz cellimmediately after mixing, and the UV-vis spectra were recorded atdifferent time intervals. The color of the solution changed gradually tolight pink within 15 min after mixing. However, some of the samples tooklonger for the color formation. FIG. 34 shows the time-dependentspectral response obtained during the growth of Au nanostructures. InFIG. 34, the graphs depict a time-dependent Au-10 reaction after (a) 0minutes (control); (b) 1 minute; (c) 2 minutes; and (d) 3 minutes. Thespectra recorded in the early stage show a broad peak at 550 nm, whichcan be assigned to the transverse component of SPR absorption. Theintensity of the peak increases monotonically with time indicating theincrease in the amount of the gold products. It can be observed fromFIG. 34 that the intensity of the UV-vis absorption peak increases up to2 min, and then increases exponentially because of the formation of theproduct. The reaction completes within a few minutes. FIG. 35 shows atypical UV-vis spectrum of gold nanostructures obtained by reducingchloroauric ions with a natural muscle-6013 (Au-10) extract. The broadSPR bands centering at 550 nm are clearly visible, which can beattributed to the in-plane dipole resonance.

Similarly, the UV-vis spectra for other compositions identified in Table8 are shown in FIGS. 36-38. In FIG. 36 curves (a) through (c) representUV spectra of (a) Au-15, (b) Au-5 and (c) Au-10 samples. In FIG. 37,curves (a) and (b) represent UV spectra of (a) Au-7 and (b) Au-12samples. Samples Au-5, Au-10 and Au-15 reveal a similar spectra to Au-3,Au-8, and Au-13 samples. However, samples such as Au-1, Au-6, Au-7,Au-11 and Au-12 did not show the absorption at 550 nm.

Representative XRD patterns of the gold nanostructures synthesized bydifferent plant extracts are listed in Table 8 and found in FIG. 39. Anumber of Bragg reflections were present which could be indexed on thebasis of the face-centered cubic (fcc) gold structure. No additionalimpurities were found except a broad hump around 2θ 20⁰ . The broad humpmay be from the organic moieties present in the extract. The XRD patternclearly shows that the gold nanostructures are crystalline. In addition,the intensity of the (111) diffraction is much stronger than those ofthe (200) and (220) diffractions. These observations indicate that thegold nanostructures formed by the reduction of Au(III) by plant extractare dominated by {111} facets, and hence more {111} planes parallel tothe surface of the supporting substrate were sampled.

Scanning electron microscopy was used to understand the surfacemorphology of the Au nanostructures. SEM images of samples (a) Au-1; (b)Au-2; and (c-d) Au-4 samples are found in FIG. 40. Sample Au-2 formedspherical nanostructures with sizes ranging from 100 to 300 nm. Au-1 andAu-4 also yielded a few spherical nanoparticles along with prisms andhexagonal structures. (See FIGS. 41 and 42.)

Similarly, Au-11, and Au14 samples yielded mainly prisms and hexagonalAu nanostructures along with small amount of spherical particles. Thesame trend continued for Au-6 and Au-9 samples. The samples of Au-10 andAu-12 consist of spherical particles with sizes ranging from 100-200 nm.

Typical TEM images revealing the size and morphology of the goldnanostructures are given in FIGS. 43 and 44. The nanostructures range insize from about 20 nm to more than a micron in diameter, depending uponthe extract used for the preparation. Different shapes such as sphericaland hexagonal geometries with very smooth edges were observed. Thesingle-crystalline structure of these nanostructures was furtherconfirmed by their corresponding electron diffraction patterns. FIG. 45show the TEM image of isolated nanostructures obtained using Au-1, Au-2and Au-5 samples, respectively. The Au-1 sample yielded interestingplate stacks whereas Au-2 sample yielded mixed prisms, rods andspherical particles. The Au-5 sample was observed to form only sphericalnanoparticles with sizes ranging from 20-50 nm. Similarly, TEM images ofAu-3 and Au-4 at lower and higher magnification is shown in FIG. 45. theAu-3 sample yielded only spherical particles, in contrast to the Au-4sample, which mainly formed prisms and hexagonal structures.

Au nanostructures were also made using commercially availablesurfactants such as butyl ammonium bromide. The reaction between butylammonium bromide and HAuCl₄ is spontaneous and color changes from paleyellow to orange (see FIG. 46 for XRD pattern). The XRD pattern afterimmediate reaction did not show any peaks corresponding to Aunanostructures (see FIG. 46( a-b). However, the overnight reacted samplehad peaks which can be indexed to cubic Au pattern. The pattern wascompared with JCPDF card no 00-004-0784.

The embodiments illustrated and discussed in this specification areintended only to teach those skilled in the art the best way known tothe inventors to make and use the invention. Nothing in thisspecification should be considered as limiting the scope of the presentinvention. All examples presented are representative and non-limiting.The above-described embodiments of the invention may be modified orvaried, without departing from the invention, as appreciated by thoseskilled in the art in light of the above teachings. It is therefore tobe understood that, within the scope of the claims and theirequivalents, the invention may be practiced otherwise than asspecifically described.

1. A method for making one or more metal nanoparticles, comprising:providing a solution comprising a first metal ion; providing a plantextract that comprises a reducing agent, a polyphenol, caffeine, and/ora natural solvent or surfactant; and combining the first metal ionsolution and the plant extract to produce metal nanoparticles; whereinthe metal is selected from the group consisting of iron, manganese,palladium, copper, indium, and combinations. 2-9. (canceled)
 10. Themethod of claim 1, wherein the providing of the solution comprising thefirst metal ion, the providing of the plant extract, and the combiningof the first metal ion solution and the plant extract to produce metalnanoparticles are conducted at about room temperature.
 11. The method ofclaim 1, wherein the reducing agent, polyphenol, caffeine, and/or anatural solvent or surfactant is selected from the group consisting oftea extract, green tea extract, coffee extract, lemon balm extract,polyphenolic flavonoid, flavonoid, flavonol, flavone, flavanone,isoflavone, flavans, flavanol, anthocyanins, proanthocyanins,carotenoids, catechins, quercetin, rutin, and combinations. 12.(canceled)
 13. The method of claim 1, wherein the plant extract isobtained from a waste product selected from the group consisting offruit juice pulp, fruit juice manufacturing wastewater, fruit juicemanufacturing waste, food processing waste, food processing byproduct,wine manufacturing waste, beer manufacturing waste, and forest productprocessing waste.
 14. The method of claim 1, wherein the natural solventor surfactant is selected from the group consisting of VeruSOL™-3,Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3 (CB-3),EZ-Mulse, and combinations.
 15. The method of claim 1, furthercomprising: providing a second solution of a metal ion, and combiningthe first metal ion solution, the second metal ion solution and theplant extract to produce metal nanoparticles comprising first and secondmetals. 16-21. (canceled)
 22. The method of claim 1, wherein the metalion is an iron ion.
 23. The method of claim 1, wherein the solutioncomprises ferric chloride (FeCl₃), ferrous sulfate (FeSO₄), ferricnitrate (Fe(NO₃)₃), Fe(III)-EDTA, Fe(III)-citric acid, Fe(III)-EDDS,Fe(II)-EDTA, Fe(II)-citric acid, and/or Fe(II)-EDDS. 24-41. (canceled)42. The method of claim 1, wherein the first metal ion is present in amedium to be treated.
 43. The method of claim 1, wherein the first metalion is provided in a medium to be treated by adding a chelating agent toa soil and/or water sample to be treated.
 44. (canceled)
 45. Acomposition comprising zero valent metal nanoparticles and a plantextract or component of the plant extract that comprises a reducingagent, a polyphenol, caffeine, and/or a natural solvent or surfactantwherein the metal nanoparticles comprise one or more of iron, manganese,palladium, copper, indium, and combinations.
 46. The composition ofclaim 45, wherein the metal nanoparticles are coated with a substancederived from the plant extract. 47-50. (canceled)
 51. The composition ofclaim 45, wherein the metal nanoparticles are substantiallynon-aggregated.
 52. The composition of claim 45, comprising a naturalsolvent or surfactant.
 53. The composition of claim 52, wherein thenatural solvent or surfactant is selected from the group consisting ofVeruSOL™-3, Citrus Burst 1 (CB-1), Citrus Burst 2 (CB-2), Citrus Burst 3(CB-3), EZ-Mulse and combinations.
 54. The composition of claim 45,further comprising a chelating agent.
 55. (canceled)
 56. The compositionof claim 45, further comprising an oxidant.
 57. (canceled)
 58. Thecomposition of claim 45, further comprising a carboxy methyl cellulosecoating or a hydrophobic coating on the surface of the nanoparticles.59. (canceled)
 60. The composition of claim 45, wherein the metalnanoparticles comprise zero valent metal and a component of the plantextract.
 61. (canceled)
 62. The composition of claim 45, wherein themetal nanoparticles comprise at least two different metals. 63-88.(canceled)
 89. The composition of claim 45, wherein the metalnanoparticles are coated with a phenolic compound of the plant extract.